Picture of Super Secret Lock Box w/ Capacitive Touch
Hey everyone, I wanted to share a project I just finished up. I built a super secret locking box for my girlfriends little brother. He has a knack for creative lego building so I thought it would be a good idea to open him up to the Arduino as soon as possible. The super secret locking box will only open for those with right password or there is a hidden way to reset the passcode so that no prying little sister would ever be able to figure it out. That is, unless she finds this instructable. The secret method involves using some capacitive touch sensing. 

The Arduino stays asleep to conserve battery and only wakes when the button is pressed. Upon waking, there are two paths to go down, flash the green LED, unlock, and go back to sleep OR light up the red LED and wait for 20 seconds for the right passcode, then go to sleep. In the period before it goes to sleep, if you touch(not press) the button for 5 seconds, the passcode will be set to whatever the code is currently. It will then unlock and go back to sleep. The 20 seconds timer restarts every time the button is pressed.

ATmega168/328 on a PCB or an Arduino with a breadboard
Wood Box
small servo
3x Potentiometers & knobs
push button
2x 100 ohm resistors 
150 ohm resistors 
battery pack
depending on how you make the latch, these parts will be up to you, I used 1/4" square dowels to make the latch and supports 

Skills with a Dremmel
Soldering Iron
Hot Glue Gun
Wood Glue (I recommend Gorilla Wood Glue, the non-foaming kind)

If anyone can decipher the suspected Japanese characters, I would really love to know the original purpose of the box.

He loved it! 
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boompjes 10 months ago
Hey , ryclmer!

Nice Instructable, I'm planning to make this project myself. But what library's did you include.
rclymer (author)  boompjes 10 months ago

#include <Servo.h>

#include <CapacitiveSensor.h>

#include <avr/sleep.h>

boompjes  rclymer8 months ago

I can't find a download link for the "avr/sleep" library, could you give me a download link please.

rclymer (author)  boompjes 8 months ago

It think its a built in feature, no need for download.

boompjes  rclymer10 months ago

Thanks rclymer

Awesome! nice job!

bosko19781 year ago

thank you so much for doing this. I want to build this with my son. Can you please put up part numbers for some of the stuff? Especially the pots? Where did you get knobs like that?

rclymer (author)  bosko19781 year ago

Thanks so much, I'd be glad to help you find some of the same parts. Everything came from either ebay or amazon.

pots ~ http://www.ebay.com/itm/271315681087?ssPageName=ST...

knobs ~ http://www.ebay.com/itm/290803952185?ssPageName=ST...

button ~ http://www.amazon.com/gp/product/B0094FPJ4O/ref=oh...

servo ~ http://www.ebay.com/itm/SG90-Mini-Gear-Micro-9g-Se...

hnee47111 year ago
Those are Chinese Character, not Japanese. You also have it upside down in the photo. The words means incent dispensing device. So I assume this is a storage box that stores some form of incent dispensing device.

This is a link to a page with many pictures of antique units of what the original device inside might look like. http://www.baike.com/wiki/%E9%A6%99%E5%85%B7

are they simplified characters? if not they could be either chinese or japanese (kanji). but yeah, upside down box for an incense burner.
hpb1 year ago
Very clever! how did you build the capacitive touch switch? i've been trying to get that working right for another project but its too erratic and touch input read have a high error rate.
rclymer (author)  hpb1 year ago
All the capacitive touch is taken care of in code. The library does all the hard work. I soldered a jumper to the nut on the screw to make contact with your finger. You will have to use the serial monitor and fool with the values the sensor returns and set a threshold that triggers the timer. If you are using a laptop, make sure it is plugged in. A laptop not grounded will give you inconsistent readings.
emerystora1 year ago
My 15 year old grandson has been teaching himself Japanese. He says the picture of the characters is upside down. The first one is "fragrant" and the second one can refer to several things. One is "sapling" So it appears that the box was for a plant with the "cover" on the bottom.
Not knowing Japanese I would have guessed that the symbol on top is "man with goatee" and the bottom symbol is "happy dancing".
My friend came to a similar conclusion - http://translate.google.com/#auto/en/%E9%A6%99%E5%85%B7

I'm guessing that the "lid" here was actually the bottom of the box originally, hence the upside-down-ness of the characters.
batonas1 year ago
Excellent, I studied a little about code locks earlier and 3 dials with 10 digits gives you 1000 combinations, so you can crack it number by number in less than an hour :)
I've designed my own mechanical code lock, its still waiting in my sketchbook to be made some day :)
rclymer (author)  batonas1 year ago
Exactly right. It would be a hassle but it is quite crackable. I thought to add a 4th dial but decided it would be too cluttered and not really necessary since it is a gift for a kid. If I build one as an actual safe, it will absolutely have 4 dials. I think that makes for 10,000 combinations. Next time I will use rotary encoders for better accuracy. Thanks for the post.
4 dials first number usualy 1 becouse the code is usualy a date :D the second digit's usualy from a non long past so its 0,9 or 8 you just decresed your cracking time to minutes :D
ARVash batonas1 year ago
Social engineering doesn't diminish real security. 4 digits is good enough for most locks.
I suggest a lockout as cellphones have, after tree wrong tries it locks itself for some hours. This only applies to the patient thief without a hammer, rock or saw. :) A better way to secure is to have a hardened steelframe inside of the woodbox, another lock, these three dials plus lockout code.

(When somebody tried to steal my bike I understood that security can't be one thing, it have to work like a chain or layers.)

...oh yes, thanks a lot for this instructables!
I doubt that I'll use this method, somehow it's easier to add a key and a lock instead of arduino... yes, I know, shame on me!
batonas ARVash1 year ago
if you want security keep it a secret, no one knows, no one wants.
Kinda cool, but add a power input connection, so if the batts go dead, you can plug in a wall wart and power it up!

great Xmas gift for a kid!

rclymer (author)  spark master1 year ago
I thought about it but the battery should theoretically last for well over a year and the small pinhole should prevent you from every being locked out. Also, If he plugged in the wrong adapter, say a common12v adapter, it would destroy it, then we would require a voltage regulator, but then there will be dropout voltage and higher quiescent current consumption and would the defeat the battery saving code techniques. Batteries alone are the most efficient solution.
Good thoughts fer sure, but if you have a work around , then it is not an issue. It is a very cool project. I made my own box when I was a kid, learned a lot from my mistakes. Now I want to make one with a tumbler system and carve the top and sides and maybe archane symbology for the numbers!!

again, nice box
Commercial safes have the batteries inside a detachable control panel.
Marko2381 year ago
Nice work, I've been thinking to do something like this, don't have the box yet though. Is it possible to replace batteries from outside? Even though the batteries should last for decades, but how do you open it if they are depleted?
rclymer (author)  Marko2381 year ago
There are panel mounting battery compartments that would do that. If you watch the video, you will see I drilled a very small hole just big enough for a paper clip to push the latch open. The box is definite the hardest thing to find.
HeMa1 year ago
As Ozzie_G said the box is upside down. In Chinese the character on the bottom 香 (on the top of the box is right side up) means fragrant and 具 means tool, I imagine in Japanese it means box. The characters for Chinese and Japanese are mostly similar even if some of the meanings are slightly different.
spikec1 year ago
That's a really cool thing to build for a kid. Nice job!
rclymer (author)  spikec1 year ago
Thanks a lot. I hope he thinks it's as cool as everyone here has said it is.
cvbritton1 year ago
From the WikiPedia: Diode:

For silicon diodes, the built-in potential is approximately 0.7 V (0.3 V for Germanium and 0.2 V for Schottky).
rclymer (author)  cvbritton1 year ago
Thanks for input. That will save a lot of trial and error later on.
elvisjrteo1 year ago
me likey!
rainbowbr1 year ago
This is an excellent instructable, just curious how much did it end up costing you?
rclymer (author)  rainbowbr1 year ago
I'm glad you like it. It costs me about $50 but that is also including the extra parts leftover. Everything but the box came from eBay or amazon. Here is a rough list of parts and prices
Box - $20
Button - $5
RGB LED - $1
Pots - $4
9g Servo - $4
ATmega328 - $3
PCB board - $1
Battery pack - $4
wire - $3

i think u might wanna put the code that typed out into a library so pple can just down load it.
I didn't prove the store wrong. These characters are used in both Chinese and Japanese. (Japanese has additional character set)
My Chinese is very poor. The box may have contained incense or something that incense is used in. A ceramic container with holes in it through which the smoke can escape for example.
Did you attach the hinges, or did the box normally open in this way?
It looks as if the "box" was actually the cover and what you now use as a lid was a bottom.
So perhaps something pretty was standing on the bottom and could be covered by your box when not in use.
rclymer (author)  Ozzie_G1 year ago
Yes, I was thinking the same thing. The lid was probably was used as a platform. It came with a strap through the holes in the lid and you can see where they have worn out the finish in a V shape. To me, that confirms your theory.
rclymer (author)  astral_mage1 year ago
Yeah, that was the plan, I am getting an error when I try to upload it. So for now copy & paste is the best Ive got.
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