How to make a automated hidden compartment?

[nofinga911]

How can I make a compartment that has a drawer that opens with a switch? I just need the basic idea of how this would be done. Thanks

 

[#12]

The simplest way is to use an electromagnet, if you ask an electronics forum. If you ask a woodworking forum, you'll get woodworking answers.

 

[nofinga911]

That sounds interesting. Can you explain how I would use it to open and close a small drawer?

 

[#12]

Well, magnetism attracts things that are made of iron or steel. Electromagnets can be turned on or off with a switch. If you place a piece of steel in a way that stops the drawer from being opened, you can switch on an electromagnet which pulls the steel out of the slot so the drawer can be opened.

The electrical part is the easy part. It's the "hidden" part that is difficult.

 

[SABorn]

Perhaps you could gutter an old CD Rom from a computer and use the guts of that to open/close a small drawer.

If you have enough depth behind the draw you could just attach the front panel of the CD Rom to the back of the drawer.

Most use a very small DC motor to drive the carriage in/out.

Another way would be to use the carriage drive from a old bubblejet printer as these have a belt drive that could be used.

Many ways to do it but it all comes down to how clever you are at adapting things.

Pete.

 

[nofinga911]

Well, magnetism attracts things that are made of iron or steel. Electromagnets can be turned on or off with a switch. If you place a piece of steel in a way that stops the drawer from being opened, you can switch on an electromagnet which pulls the steel out of the slot so the drawer can be opened.

The electrical part is the easy part. It's the "hidden" part that is difficult.

That sounds really good but I really wanted to make it automated so the drawer opens and closes when the switch is pressed. Any ideas on that?

 

[Boncuk]

You could use a small motor with a pinion and and gear rack mounted to the drawer as used for sliding gates.

The drive will work fine provided the drawer moves on ball rails which are used for furniture.

Mount the motor with the pinion as close as possible at the front end of the drawer to avoid an overly long gear rack.

Use limit switches and a control circuit reversing the motor to be operated with one button.

Boncuk

 

[RMMM]

A pulley system with a standard motor can also work.

A small reverseable DC motor and a DPDT relay to reverse it. Throw in 2 limit switches to "know" when its fully opened and fully closed, and you are mostly there.

Depending on the drawer size, and the distance of travel, a spring system could still be used to push the drawer open as the spool unwinds the "retract" string/cable

 

[transistor495]

Well, magnetism attracts things that are made of iron or steel. Electromagnets can be turned on or off with a switch. If you place a piece of steel in a way that stops the drawer from being opened, you can switch on an electromagnet which pulls the steel out of the slot so the drawer can be opened.

The electrical part is the easy part. It's the "hidden" part that is difficult.

You mean a 'controlled electromagnetic attraction'?

Else it'll be horrible for the user of hidden compartment I think

 

[nofinga911]

That could work, I am going to look into that a little further, thanks Boncuk.

 

[nofinga911]

That sounds good too, how would I make the retractable cable system and spring system? What type of parts would I need?

 

[RMMM]

That sounds good too, how would I make the retractable cable system and spring system? What type of parts would I need?

A standard drawer setup with a spring behind the drawer trying to push it open at all times.

You would have a motor with a spool of cable/rope on it. The cable end would be connected to the drawer.

As the motor un-winds the cable, it allows the spring to push the drawer open.

Reverse the motor to wind the cable back up, pulling the drawer back in.

Consider the drawer a fish, and the motor a fishing rod reel. You will be REELING the drawer back in.

You should have limit switches so the motor knows when to stop winding and unwinding.

 

[Boncuk]

Hi nofinga911,

you could of course use a retractable cable and spring system. The advantage would be fast opening of the drawer if you use some kind of clutch to engage the reel when pulling the drawer into the closed position.

On the other hand you certainly don't want the contents of the drawer to be pushed forward when the drawer hits the mechanical stop (the same what happens if you hit a concrete wall with your car ).

The pinion gear method takes care of smooth movement in and out and omits one part with lots of wear and tear (spring), which must be almost as long as the travel of the drawer.

Boncuk

 

[RMMM]

The drawer would open as slowly as the motor unspooled the line.

A small geared motor would be enough. Find a happy speed.

I agree, If I were doing this, I would do the CDRom tray idea.

 

[Boncuk]

The drawer would open as slowly as the motor unspooled the line.

A small geared motor would be enough. Find a happy speed.

I agree, If I were doing this, I would do the CDRom tray idea.

What do you think about the power necessary to open a drawer?

The small tray drive can't push and pull heavy loads (more than 250g).

Boncuk

 

[RMMM]

I mean the idea...not the exact parts.

I was thinking along the lines of cutting an automotive V-belt and laying it down as the rack gear, affixing it to the bottom or side of the drawer, then using a geared motor, find a drive gear whos teeth fit the teeth on the v-belt. Wallah! 1 super sized cdrom tray

 

[SABorn]

He did say a "Small" drawer thats why i said a CD rom.

As for the cog belt idea, well that was what i was saying with using an old bubble jet printer carriage drive, as they have a cog belt and small DC motor ( or stepper in real early models) with a cog pinion drive on them.

Old printers are every where and free, with lots of extra goodies like photo interupters, and photo encoders etc, i have used them for many projects.

Pete.

 

[nofinga911]

I mean the idea...not the exact parts.

I was thinking along the lines of cutting an automotive V-belt and laying it down as the rack gear, affixing it to the bottom or side of the drawer, then using a geared motor, find a drive gear whos teeth fit the teeth on the v-belt. Wallah! 1 super sized cdrom tray

Thats an awesome idea, nice and simple with minimal parts. So far this seems like it would work best. Now what do i use to time the motor so it only operate long enough for the drawer to open?

 

[nofinga911]

I have an old printer in the attic...i guess his time has come to get dissected...

 

[RMMM]

Thats an awesome idea, nice and simple with minimal parts. So far this seems like it would work best. Now what do i use to time the motor so it only operate long enough for the drawer to open?

Use limit switches.

Little switches that get tripped when the drawer is all the way out, and another for all the way closed.

Look up micro switches , and limit circuits.

They can open the relay coil to kill the motor when the drawer reaches the proper point. When you hit the "close" button, it will switch the DPDT relay and provide momentary power to get the drawer off of the limit switch. Then it will close automatically from that point. Stopping when it hits the "closed" limit-switch.