Introduction: Secret Drawer Lock

Picture of Secret Drawer Lock

The Secret Drawer Lock provides invisible high tech security to a dresser, or cabinet drawer. It uses a spring-loaded solenoid lock mechanism that is powered when a reed (magnet) switch is activated. It is very simple to build and rather effective. It uses a battery to power the lock mechanism, but I have also included a (optional) power port on the bottom of the drawer to be able to plug it in and activate it even if the battery dies.

Step 1: Materials

Picture of Materials

To make a Secret Drawer Lock you will need:

(x1) Solenoid lock mechanism
(x1) Reed alarm switch
(x1) 12V rechargeable DC battery
(x2) Crimp-on quick disconnects
(x1) Lock strike plate
(x2) 1/4" x 1/4" spacers (or appropriate for your project)
(x2) 1" wood screws
(x4) 3/4" wood screws
(x1) power jack (optional)
(x1) High-strength magnet hook

Step 2: Wire Connectors

Picture of Wire Connectors

Strip the ends of a piece of red and a piece of black stranded wire and crimp on two quick disconnects onto the ends of the wire. These will attach the circuit to the battery.

Step 3: Extend the Wires

Picture of Extend the Wires

Solder the other ends of the red and black wire to the two wires coming from the lock mechanism and insulate each with shrink tube. It is not remarkably important which color wire gets connected to which on the lock.

Step 4: Mount the Lock

Picture of Mount the Lock

Fasten the lock to the front inside edge of the drawer facing up.

The lock mechanism needs to be lower than the top of the drawer for this to work.

Step 5: Attach the Switch

Picture of Attach the Switch

Place the reed switch in one of the corners of the inside of the drawer close to the front.

In most cases it's best to have it backed off just a little bit because from the front of the drawer because this will make it a little bit harder to trigger. This means that you will need to have the magnet in just the right spot.

Step 6: Plug in the Battery

Picture of Plug in the Battery

Connect the quick disconnect attached to the black wire to the black ground terminal on the battery.

Connect the quick disconnect attached to the red wire to the red power terminal on the battery.

You can now use a magnet to test to make sure it works. If it doesn't, try moving the reed switch closer to the front of the drawer. If it still doesn't work, try getting a larger magnet or checking if the battery is charged.

Step 7: Power Jack (optional)

Picture of Power Jack (optional)

You don't need to do this part, but I recommend it. Should the battery ever die, the drawer won't be able to open. This plug provides a 'backdoor' to allow you to briefly apply power to open the drawer, get the battery out, and recharge it.

To wire it up, first unplug the battery. You are in for a shock (both figuratively and literally) if you don't!

Next, cut the wires that connect to the battery in half. Solder the black wires each to one of the respective outer terminals.

Solder the two red wired together to the center terminal.

Step 8: Install the Power Jack (optional)

Picture of Install the Power Jack (optional)

Drill a 1/4" hole through the bottom of the drawer, and install the power plug from the inside out.

Fasten it tightly in place with the plug's mounting hardware.

Keep in mind the power jack is installed to provide a backup power source using only a 12V plug with a positive tip connection. It is not recommended to charge the battery through the jack. You should unplug it and connect it to a charger when necessary.

Step 9: Measure to the Edge

Picture of Measure to the Edge

Figuring out where to mount the strike plate is a little bit tricky. You need to figure out where to position it so that the latch catches it when the drawer gets pushed in.

Fortunately, this can be solved with some careful measuring. Measurements tend to differ from drawer to drawer, but this is my general process.

I simply pushed the drawer all the way in and measured the distance from the inside of the drawer to the edge of the surface I am mounting the strike plate to. In this case, it is the underside of the top surface of the end table.

Step 10: Determining Strike Plate Position

Picture of Determining Strike Plate Position

Next I needed to figure out where to mount the strike plate in relation to the inside edges of the drawer.

To do this I centered the strike plate atop the lock and measured the distance from the inside front edge of the drawer to the center of this pairing. While I was at it, I also measured the distance from the side edge to the center of the lock.

Step 11: Mark for Mounting

Picture of Mark for Mounting

Once I knew all of the positioning information, I added together the first measurement with the measurement of the inside front edge to the center of the lock for a distance we will call "D". I flipped the end table over and drew a line along the underside of the top (the upward facing side) at distance "D" parallel to the front edge. This line indicates where the center of the lock will be once pushed in.

Finally, I measured over from the edge to figure out where the strike plate needed to be mounted along this line so that it would land in the center of the lock. Once I was sure, I marked the strike plate's mounting holes.

Step 12: Mount the Strike Plate

Picture of Mount the Strike Plate

Insert the drawer, and push it halfway closed.

Mount the strike plate using wood screws and 1/4" (or appropriately sized) spacers to bump it up a little from the surface of the drawer. The idea is that it should be spaced to the right height to catch the latch from the lock.

Step 13: Close the Drawer

Picture of Close the Drawer

To be on the safe side, get a magnet and test it one last time before you close it. If you close it before it works, you likely won't get it back open (without some furniture surgery).

When you are sure it is working, close the drawer.

Step 14: Hang the Magnet Hook

Picture of Hang the Magnet Hook

Hang the magnet hook somewhere nearby and disguise it by hanging something from it. No one will suspect this is the key to the drawer.

Step 15: Keep Things Safe

Picture of Keep Things Safe

Keep your things secret. Keep them safe.

When the time comes to unlock it, go pull the magnet hook from wherever it is hanging and unlock the drawer.

Comments

saderman (author)2017-02-16

Or...

Following the "Occam's Razor" theory...

http://www.homedepot.com/p/Tot-Lock-Cabinet-Security-4-Lock-and-Single-Key-Assembly-TL-13401-R/207113549

mtray (author)saderman2017-02-21

:-).... who needs a battery anyways.

ChrisP32 (author)saderman2017-02-16

But where ya gonna hang your keys. lol

gjp627. (author)ChrisP322017-02-17

cool, seen the ad, just don't have the nails for that

bgonzalez7 (author)saderman2017-02-16

That looks pretty cool. And it uses waaay less space. Still, someone can make an instructable to 3D print one :)

dollarseed (author)bgonzalez72017-02-16

Home Depot no longer stocks this item, but there are plenty on eBay. I just bought one today for a project in my shop. Thank you.

jeffc61 (author)2017-02-21

Very nice indestructible. I really like the gif showing how it works.

Two thumbs up!

mach1950 (author)2017-02-16

Never fails to amuse me how so many negative people jump on the fact that there are alternatives. This is an instructable, the germ of an idea taken to fruition and described for others to learn. It is not meant to be a unique invention. If it was, all the instructables on cake baking would be a waste of time, now wouldn't they?

This is a very well done instructable, clear, concise, well illustrated, with working links to all required components. VERY WELL DONE!!!

Thank you randolfo.

ecollen (author)mach19502017-02-21

Hi mach1950

Well said! My sentiments exactly.

booung (author)2017-02-20

Better yet...

Drill adjacent holes in the sides of the front panels of drawer close to front as possible. Insert a plastic straw to fit the outside diameter of both holes, place a slightly smaller magnetic dowel long enough to slide between the two pieces of wood to brace the slide. Activate using a strong magnet held on the wood drawer face to slide the dowel across to breach the slide so the drawer will not open. Hence a sightless lock. Blow your familys minds how you access it.

Cheers Folks!

SiddR1 (author)2017-02-20

The battery is too big.

GordonD6 (author)2017-02-16

I was reading about the old idea of credit card trick of un locking the lock.Well I'd use a dead bolt type pin.But if a lock door was made to stop a crook it'd stop the owner also with out the key.To honest "NO LOCK IS SAFE FROM THIEVES".If they want in there always away to by pass a lock.

_soapy_ (author)GordonD62017-02-17

If the thief is using a screwdriver or crowbar they'll get through the wood. However, if they don't know to spend the time and energy attacking it, they won't. Obscurity is your friend here.

Sebafleb (author)_soapy_2017-02-19

But this isn't to protect your valuables from being stolen, this is to protect your goodie stash from family.

bigpig (author)2017-02-19

Rube Goldberg would approve.

hammer9876 (author)2017-02-17

What happens when the battery dies?

mali77 (author)hammer98762017-02-19

you die

CPUDOCTHE1. (author)2017-02-17

You can purchase kid proof locks that are operated with magnets and the best thing is that they don't require batteries. Sometimes simplest is bestest.

CharlesL25 (author)2017-02-17

Do they make a 9v solenoid nice project battery takes to much space

gadgetgogo (author)2017-02-16

https://www.indiegogo.com/projects/meet-the-smart-cube-tech-that-protects-security-family#/

_soapy_ (author)gadgetgogo2017-02-17

Haha, I thought the same!

MartinL56 (author)2017-02-16

Would one Reed alarm switch be strong enough to work 2 of the solenoid lock mechanisms?

I ask; because I was wondering about being able to use this on a secret door.

_soapy_ (author)MartinL562017-02-17

There are concerns that the reed switch isn't good enough to take the current draw of even one solenoid!

Basically, solenoids draw over an amp, but most reed switches are capable of 300mA or so. Putting two amps through it would likely weld the contacts together.

You'll need a relay or a transistor/mosfet.

gjp627. (author)2017-02-17

wonderful indestructible! My only better, or other choice might be a 9mm and constant surveillance. In regards to others, the weapon of your choice. Semper Fi MFRS

BrucefromAustralia (author)2017-02-16

Good idea. Have played with reed switches since i was a kid.

If you want to follow this path, could simplify by removing reed switch, magnet & battery... just leaving electric lock, fittings & wires connected to the 'optional' power socket. Prefer not to include battery in circuit as may fail. It's just the 'KISS' principle.

Take wires from lock to low voltage socket hidden underneath or at back. Apply 12 volts only when need to open lock.

Works well with metal drawers which can't use magnet. I have used this for years with metal filing cabinets with broken locks or lost keys.

Or better, add 2 separate metal trim on wooden drawer unit connected by wires to solenoid - touch 12 volt wires to those to open. Be creative. No one would expect decorative features to electrically control lock ;-)

wannabemadsci (author)2017-02-16

Very well done instructable! Excellent photos. I like your foresight of having the back up power source jack - a very nice touch!

I reiterate the previous comments regarding the rating of the reed switch: Your solenoid draws 1.3 amps, and reed switches are typically intended for sensing (low voltage and current) applications; usually under a 1/2 amp. (Of the 530 reed switches on Digi-Key; 83% were rated a 1/2 amp or less) so there is some concern that the reed switch is not rated high enough to carry the current involved which can lead to premature failure.

The style of switch shown is typical for burglar alarm systems and would only have to carry milliamps of current; I noticed that the vendor's description of the switch did not carry any electrical ratings which is another indication that the rating is probably low.

So a word to the wise, you might want to consider replacing the reed switch with one with known ratings or use it to switch the coil of a relay that would then handle the solenoids current, as others have indicated. I'd hate for the system to fail and permanently lock your valuables in the drawer :-).

trgtdron (author)2017-02-16

OMG really? There is always someone whining about what "might" happen... Get a life. BTW DROP THE CAPS....

Well done Randofo, simple but elegant. I personally like just drilling straight down the side board into the bottom just a little then dropping a roll pin into the hole and using magnet to pull the pin up until you can move the drawer a bit then let the pin drop back down, open drawer and when you close it, pin drops back into hole until you grab it with a magnet and repeat. Kept the kids out of important stuff lol.

e5frog (author)2017-02-16

Why even use something electric, a magnet and a mechanical setup could lock it.

PaulC80 (author)2017-02-16

Brilliant project! This is the perfect way of hiding my Mrs's credit cards!!

Sorry if this is very disjointed thinking but.....

Is it possible to produce enough power by the swipe of the magnet (such as when a motor is reversed in turning the spindle to produce power) ? Or use a wireless method of transmitting power to the solenoid (same method used to charge phones wirelessly)?

This way you wouldn't have to worry about the battery discharging over time or having to connect the lock to the mains supply.

OddJ (author)2017-02-16

Or drill a hole on the top edge of the drawer about 3/16 wide and deep. Drill a matching hole under the table top to meet in closed position. Deeper than the first. Now you need a small steel bar just under 3/16" and around 3/8-1/2" long. Now the hard part. Hot glue a small string inside the table top hole to the back of the steel bar. Super glue in gel form may be easier. I'm hoping you get the gist of this by now. Gravity brings the bar down between the drawer and table top. A magnet to the table top raises the bar to allow the drawer to open. No batteries. No solenoid. Gravity and a magnet. Might be cheaper to build too. Haven't priced kitchen magnets in a while.

PHOTOM (author)OddJ2017-02-16

You can use an old hard drive magnet they will lift ten pounds or more...

RainerG1 (author)OddJ2017-02-16

Interesting and certainly cheaper. Note that after opening the drawer, you may forget to use the magnet to pull up the steel bar(or rod which is easier when drilling) before closing ... crunch! It may be possible to avoid this by cutting a small ramp in the drawer, and rounding the steel rod so it rides up the incline. Instead of a string perhaps a 1/4" long thin walled tube/pipe(or drilled out nut) with a screw dropped inside to act as the rod (screwhead stops it from falling out when drawer open and magnet removed). Press fit or glue the tube in the tabletop with sufficient play for the screw 'rod' to rise and fall.

ilpug (author)2017-02-16

This is a great idea. I have made hidden magnetic locks before, but not electronic. Several metal pins in vertical holes that get pulled into place by gravity when the magnet is removed work great, provided the piece of furniture being locked is either wall mounted or too big to easily flip over and disengage the lock. Your design works in any orientation though, so is superior for smaller projects.

tntartglass (author)2017-02-16

Wouldn't it open just by sliding a credit card along the drawer edge?

ChrisP32 (author)tntartglass2017-02-16

no because it is not faving that direction

treymartin82 (author)2017-02-16

For a small drawer this size or maybe a touch bigger would you suggest a battery or the connected power option??

nealalan (author)2017-02-16

Love this!!!! Think I'll go the route of a USB port and only using an external USB battery. Save mucho space and double security. :D

Any thoughts how well this would work on a metal drawer? The magnet could always be there and just move it for a second! ;)

443300889588 (author)2017-02-16

Nice idea, but with one flaw. The solenoid runs at 1.3A and the reed switch would typically have a rated maximum current of 0.5A. The easiest solution would be to put a small 12v relay (less than $1 on aliexpress) in with the reed switch activating the relay which then switches the solenoid.

randofo (author)4433008895882017-02-16

A relay would be on the safer side.

However, typically these switches are rated at a much higher voltage than 12V (typically around 100DC), and even if the solenoid draws it's maximum current, it is only for a very brief energizing period. The typical solenoid operating current flowing across the switch is smaller. I have been using this without issue for a while, and I think it is likely fine.

eGadgetGuy (author)randofo2017-02-16

I would want you to be careful. these are rated 100V but only 10W which flies in the face of their 0.5A rating. but 10W is not enough and one day you may pay the price if the reed switch burns out or catches on fire!

http://a.co/5qBlA0M

eGadgetGuy (author)4433008895882017-02-16

yes, I would agree. but you do need to look at power rating. If the reed switch is rated 24V @ 0.5A this is much closer to the 12V @ 1.3A but still not enough. However if the reed switch is rated at 120V @ 0.5A then all bets are off.

12V* 1.3A = 15.6W

12V * 0.5A = 6W

24V * 0.5A = 12W

120V * 0.5A = 60W

Just my $0.02

mgrey (author)2017-02-16

This is awesome, but to save having to use a battery I suggest using a magnetic latch like the one used here: https://www.instructables.com/id/Secret-Compartment-Floating-Shelf/

BlackoutXIII (author)2017-02-16

Nice instructable, but couldn't you just use a magnetic cabinet lock, like those used for childproofing a kitchen? They're much simpler, don't require a battery, cheaper, and take up less space within the drawer.

https://www.amazon.com/Safety-Baby-Magnetic-Cabinet-Locks/dp/B00PV6H3Z8

eGadgetGuy (author)BlackoutXIII2017-02-16

Nice idea. Much simpler.

Not to take away from the OP, because there may be other ways to make this more secure, like adding some type of coding or using 2 gap switches so you have to apply 2 magnets...

kkmmccoy (author)2017-02-16

very cool the one flaw is there is not a lot of space for anything you want to put in there

gm280 (author)2017-02-16

Nice idea and project. You do know they make magnetic latches without the need for electricity for just this setup.

MatH2 (author)2017-02-16

fyi, You can do this without power... Beyond that of magnets I mean...

legoloverman (author)2017-02-16

thats cool

3366carlos (author)2017-02-15

awesome

cteixeira85 (author)2017-02-15

this is a great idea.. thanks for sharing

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Bio: My name is Randy and I founded the Instructables Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to ... More »
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