The Reverse Geocache™ Puzzle

The "Reverse Geo-cache" Puzzle

Fig. 1 - The Box

[Author's note: This post is the first in a real-life story that ultimately took a full year and four chapters (1, 2, 3, 4) to tell. Read them all, then browse through the other surprising puzzle box stories that have popped up along the way.]

Early this summer, the friend who first introduced me to Arduino amazed us with the news that he was moving to France to get married. Once I recovered from the surprise, it occurred to me that putting together some sort of Arduino-based wedding present might be a uniquely fitting thanks for his years of friendship and for helping get me started in this delightful enterprise. And so after weighing several ideas — I didn’t fancy adding some ugly techno-junk to the pretty collection of tea cozies and china sets — I finally settled on building the device I describe here: a puzzle box that won’t open until it is taken to a certain location.

To better understand my conception, let’s fast forward and imagine the gift opening. The new couple, freshly back from their honeymoon, remove the wrapping to reveal a book-sized wooden box elaborately carved with elephant images. (I didn’t carve it; I bought it that way at World Market.) Mounted into the lid, perhaps incongruously, are an illuminated button, a small display, and a mysterious module that sharp-eyed readers might recognize as a GPS. There’s also some kind of connector tucked away on the box’s left side. More about that later.

What do they make of all this? It’s hard to guess, but naturally I imagine they might try to open it up and take a look inside. When they do, however, they find the lid stuck tight — it seems to be latched from the inside. Will they push the button? Pretty buttons are awfully hard to resist, so let’s assume so. The blue display fires up and displays a friendly, personal greeting:

Bonsoir, famille Immel!
This is attempt 1 of 50.


Now they don’t know this yet, but the box’s embedded electronics require a good GPS fix – something that’s probably hard to come by inside a Parisian apartment. And so the display flashes “SEEKING SIGNAL” for a couple of minutes and gives up.

No signal acquired...
Powering off...

Now my hope is that they’ll realize they need to take the box outdoors or near a window. Is that a stretch? I don’t think so. My friend is a patient fellow with an engineering background, so I expect he will at least try moving it before throwing it against the wall or chiseling off the hinges. Let’s assume, then, that they go outside and push the button again. This time the series of messages is different:

This is attempt 2 of 50.
Distance 391km
*Access Denied*
Powering off...


Fig. 2 - Distance 391km

Fig. 2 - Distance 391km

Hmm. What does “Distance 391km” mean? “Access Denied” suggests that getting inside the box is indeed the objective of all this button pushing. Just for fun, let’s try again.

This is attempt 3 of 50.
Distance 391km
*Access Denied*
Powering off...

Uh oh. We seem to be consuming our limited supply of “attempts”. The “No signal” problem seems to be solved, but the message “Distance 391km” remains puzzling. Does the box know its own location? Is there something 391 kilometers away? London? The Hague? A circle of that radius drawn around Paris intersects quite a few interesting places in France, England, Holland, Switzerland, and Germany.

Knowing my friend, he will eventually think to move the box to a new location to see how the message changes. Let’s imagine, then, that he hops in his car and motors down the A11 to the famous city of Le Mans, about two hours to the southwest. After a brief tour of the cathedral and a snack at a sidewalk café, he pulls the elephant box from his backpack and pushes the button again.

This time the display is once again slightly different:

This is attempt 4 of 50.
Distance 226km
*Access Denied*
Powering off...

Aha. We seem to be getting somewhere. If we are in fact looking for a specific place, it would appear that it is 391 kilometers from Paris but only 226 from Le Mans. As you can see by the map in Figure 3, there are only two places on earth that meet these criteria – a spot just off the northern Brittany coast, and a rural area in the southwest near Bordeaux. And, as my friend is aware, one of these can be quickly eliminated simply by taking a third “reading” in a new spot.

Fig. 4 - and a circle around Le Mans

Fig. 3 - Circles around Paris and Le Mans

I suspect that from here things will proceed relatively quickly. My friend will triangulate that the “magic spot” is Île-de-Bréhat, a tiny island just a short ferry ride off the northern coast of Bretagne. If and when the couple do bring the box here, they’ll be greeted with a congratulatory “Access Granted!” and the whir of a motor announcing that the treasure inside is about to be finally revealed!

Fig. 5 - The box is unlocked!

Fig. 4 - The box is unlocked!



The electronics for this project are fairly simple. At the core, of course, is the Arduino, surrounded by a handful of devices that talk harmoniously through various native and third-party libraries. The peripherals are wired to a custom “shield” that I soldered together. The shield design makes the system modular and easy to disassemble for moving. Power is provided by 4 AA lithium batteries mounted in the box’s interior.

Major components

Fig. 6 - Arduino and the custom shield

Fig. 5 - Arduino and the custom shield

1 Arduino Duemilanove
1 USGlobalSat EM-406A GPS module
1 8×2 blue backlight HD44780 LCD
1 Hitec HS-311 servo motor
1 illuminated pushbutton
1 low voltage Pololu power switch
1 2.5mm female DC power connector
1 Adafruit Arduino prototype shield
1 ornamental box

Minor components

1 severed chopstick used as latching dowel
3 #14 eyelet screws
1 Battery pack with 4xAA lithium batteries
Various mounting screws and glue
Wire, headers, solder, and other circuit connecting items

I designed this project to last a long time. The batteries are locked inside the box and can’t be replaced if they run down — not while the puzzle remains unsolved, anyway — so it’s important to conserve power. That’s why a given “session” lasts at most 2-3 minutes before the system powers off. Furthermore, the owner is allowed only 50 attempts to discover the box’s secret, so the active lifespan of the batteries need be no more than about 150 minutes. Between sessions, the electronics draw virtually no power and should last idle for years.

Fig. 7 - The tiny Pololu switch

Fig. 6 - The tiny Pololu switch

The secret to this power conservation is the clever little Pololu switch, which gives a circuit the ability to completely turn itself off through software. When you push the button, it latches and distributes power to the system. When the sketch decides it’s time to shut down — either because it can’t find a GPS signal or it’s not close enough to the target — it simply brings the Pololu’s power control pin high, cutting power. In this “off” state the switch draws just 0.01 microamps.

Fig. 8 - The EM-406A GPS module

Fig. 7 - The EM-406A GPS module

Like most GPS units, the EM-406A generates a stream of NMEA position data. This stream enters the Arduino via a “soft” serial port managed by my NewSoftSerial library. The NMEA data is parsed into latitude/longitude using TinyGPS, a popular library I built especially for this project. If the GPS is getting a good fix, the box can determine its location within 10 meters and, through a simple calculation, how close it is to the target.

Fig. 9 - The 8x2 Liquid Crystal Display

Fig. 8 - The 8x2 Liquid Crystal Display

The display is an HD44780-compatible device controlled by the Arduino LiquidCrystal library. I wanted to incorporate some visual effects like flashing and scrolling, so my sketch contains several custom display routines. These were carefully written so as not to block the all-important serial input stream coming from the GPS.

Fig. 10 - The interior showing chopstick latch

Fig. 9 - The interior showing chopstick latch

The internal latch is built around a Hitec servo, three eyelet screws, and, as a sentimental salute to the little Chinese restaurant my friend and I used to eat at, a dowel made from one of its chopsticks. One chopstick end is attached to the servo arm, and the other threaded through the two eyelet screws mounted into the box bottom. The servo operates in one of two positions – “open” and “closed”. When instructed to close, it drives the chopstick laterally through a third eyelet screw hanging from the box lid. At this point, the box is latched. Once the puzzle is finally solved, the servo pulls the chopstick back, and the box can again be opened.


The box is running the Arduino version 0016 framework. The sketch I wrote uses native libraries Serial, Servo, and LiquidCrystal, as well as several of my own: TinyGPS, NewSoftSerial, PString, Streaming, and Flash. My libraries are freely available for download at

Conceptually, the software is fairly straightforward. At power up, the system hunts for a GPS signal. If it detects that the box is within 2 kilometers of the target spot — in this case the center of the little island — it unlocks the latch. Otherwise, it displays the somewhat cryptic “Distance: nnn km” and keeps the latch firmly locked.

How the software works

How the software works

Fig. 11 - A fake voltage overload

Fig. 10 - A fake voltage overload

The Back Door

It may seem risky to create a device that can only be activated a limited number of times before it locks permanently. What happens if the bride’s four-year-old gets hold of it? What if the batteries unexpectedly run out? What if, despite all my care and attention, there are still bugs in the implementation? Will the treasure inside be forever sealed? To address these concerns, I built a “back door” into the design. This is where the mysterious 2.5mm coaxial connector to the left in Figure 1 comes in.

If you apply some current here at a reasonable voltage, the system will power up just as if you pressed the button. But since this circuit bypasses the Pololu switch, when the box claims to be “Powering down”, it is actually lying. Instead, after a two-minute delay, the latch opens, regardless of where the box is actually located. This gives the sheepish designer (me) emergency access and one more chance to replace the batteries or repair the latest design flaw.

You might question whether it’s a good idea to leave such a gaping back door. After all, it’s a lot easier for my friend to open the box by simply plugging it in than driving it the 391 kilometers to Bréhat. Quite true. So to dissuade him from snooping too far down this path, I built in a few frightening messages. Remember, he has no idea how to use this “back door” or what voltage and current to apply. If he does figure out how to power the box this way, I feel fairly confident that whatever satisfaction he gains will rapidly disappear when the LCD starts flashing the completely fake warnings

Excess Voltage!
Remove Power!

And if these aren’t discouraging enough, they are followed by a blast of random “garbage”, suggesting that a critical failure is underway. (See Figure 10.) Whoever opens the box this way will have to stare at these ominous characters for a full two minutes.

Last minute disasters

Just a couple of days before I left for France I made a pretty serious mistake. At the time I had completed the physical construction and was just beginning the first full-scale closed-lid tests. Everything was going swimmingly – so smoothly, in fact, that I became a bit cavalier about my methodology. To address an intermittent problem, I made the last-minute decision to upgrade my system software. Reflecting back, I should have done plenty of preliminary “open box” tests before sealing it up; instead, riding the wave of my enthusiasm into disaster, I uploaded the new version, confidently closed the lid, and pressed the button. The latch engaged normally, but then the whole system went haywire. The motor began jerking crazily and the LCD limped along, displaying dimly only the top halves of each message. Soon I discovered that I had locked myself out of my own box and that disassembling it was the only way to recover. Because I had designed it to be somewhat tamper proof, this was far from easy. Ultimately, I had to break a bracket to get a screwdriver far enough into the interior to pry open the latch.

In France I had left myself just one short day to reassemble the box (which had been taken apart to increase my chances with airport security), run some last-second tests, and perform the final reset. When it came time to rearm it, something you do by connecting power to the “back door” for four minutes, I found that I had brought the wrong power supply with me. I fruitlessly combed the house I was staying in for a telephone or router with a 2.5mm connector, and then tried desperately to locate the French equivalent of a Radio Shack. After my panic subsided I realized I could just jimmy up what I needed with a couple of paper clips. It wasn’t pleasant or easy to hold those clips in place for four minutes, but I finally did manage to rearm the box with mere hours to go.

Frequently Asked Questions

What happened when they unwrapped the box?

The day after the wedding, the bride’s family hosted a brunch in the back lawn of their beautiful country house. I hadn’t expected to be present at the opening, but at one point I noticed some furtive activity in the corner of the lawn and saw that the box was being passed around, accompanied by much head scratching and gesturing in my direction. My friend, who had apparently already consumed three “attempts”, was darting back and forth exhorting everyone in halting French “Ne poussez pas le bouton!” (“Don’t push the button!”). To his dismay, his new father-in-law didn’t understand and pushed it anyway. Several people approached me to ask questions about the box, which I apologetically declined to answer. At one point a friend of the family, a charming gentleman from up the street, said to me with a thick accent, “You are — how you say in English? — a BASTARD!” That one comment made this whole project worthwhile. As of this writing I do not think they have yet managed to open the box.

What did you put inside?

With all the electronics, there wasn’t much room inside the box for anything too substantial. I put in a few local (US) gift cards to entice them to visit soon, a set of Kazuo Ishiguro audio books (on a USB key), and an overly sentimental card. And of course, as I pointed out in the card, if either of them fancies doing a little Arduino development, there’s a perfectly good Duemilanove to play with, not to mention an LCD, a servo, and a GPS.

How did you choose the target location?

Île-de-Bréhat, a charming island where motorized vehicles are prohibited, is a special place for this couple. It was while my friend was filming a movie here that he first began to realize his feelings for the young lady starring in it. And she for him, if I understand correctly. To help matters, the bride’s family owns a house here, making it a doubly attractive destination. (I may be a bastard, but I’m not going to make them travel 400 kilometers to some random, isolated location just to open a few gift cards.)

How did you get it through airport security?

I worried a lot about this. At first, when I was not certain whether I would be able get to France to attend the wedding, I had thought to present them the fully “armed” box while they were visiting the US. Fortunately, someone pointed out the foolishness of this idea. Can you imagine the interview at airport security when the hand soldered electronics show up in the X-ray?

Sir, did you pack this yourself?– No.

What’s inside?– I have no idea.

Can you open it please?– Nope.

Eventually, I decided that the best strategy was to disassemble it as much as practically possible and hope that none of the individual pieces were sufficiently suspicious to warrant being detonated on the tarmac. This seemed to work. I brought the disassembled box on two major trips without a hint of trouble.

Why limit the number of attempts to 50?

Two reasons. First, a puzzle is just more exciting if it is bounded. If it’s fun to solve a Sudoku, how much more fun is it to try and do it in under ten minutes?

The second reason is a practical one. I needed some way to make sure that power consumption would not end up being a problem. How disappointing would it be if, after all the work I put into it, the batteries ran out and the puzzle was ruined? Constraining the number of attempts helps ensure that this won’t be an issue.

The number 50 has no special significance. 25 or 20 would probably have worked just as well.

Why the 2000-meter tolerance?

There is always a little bit of error in a GPS reading, so some tolerance is necessary. The island is about 4 kilometers across, so setting the tolerance at 2000 meters forces them to actually ferry across to it without constraining them to any particular part.


The box is unwrapped

The box is unwrapped

Building this project was a joy. It was rewarding to conceive of a relatively unique GPS application and to work through the various problems as they arose. Designing the latch, for example, was a challenge I spent a good deal of time on. My experience solving mechanical problems is fairly limited, but I’d like to think that the next time I build something with a mechanical component I’ll be able to approach it with a little more savvy. Meanwhile, when you think about all the cheap sensors, displays, lights, motors, modules, radios, and buttons you can attach to an Arduino, you realize that imagination is the only constraint on the kinds of projects that can be built. This little box is a novel way of combining a GPS, a servo, a button and a display. How many more marvelous combinations lurk out there, if only someone has the imagination to put them together the right way?

[Make sure you read the sequel to this story when you're finished here.]

Page last updated on January 10, 2011 at 8:54 am
269 Responses → “The Reverse Geocache™ Puzzle”

  1. Mikal

    12 years ago


    My answering your questions involved no patience whatsoever. I’m enthralled with this project (as you could probably tell), and every question answered is that much more pleasure for me. Low-tech is beautiful. How do you build a confetti shooting box anyway? I’m glad you have the insight into human nature: we love to play!

    Best wishes,


  2. Michael B.

    12 years ago

    Dear Mikal,

    The Confetti box was just a small battery operated hand fan with it’s blades placed through the bottom of a disposable foam bowl filled with confetti. (Imagine making a cake without adding the liquid ingredients, and switching on the electric mixer. The dry ingredients fly will out!) Opening the box plucked out a small piece of paper from a clothespin, which was wired to complete the fan’s circuit. I actually had to make them in bulk. I needed 30 of them for holiday gifts. They had chocolates in the bottom. Also, my wife set a budget, but I was able to do them for less than $5 apiece (minus chocolates). There have been 2 other designs since then, but they are a little hard to describe in text.

    BTW I’m making progress on my reverse Geocache box! Thanks for the inspiration!

  3. >---^---:)

    12 years ago

    I have been geocaching for six years and love your idea.
    Please keep us all posted on how it turns out.

    Rick >—^—:)

  4. Chris

    12 years ago

    Hi Mikal,
    I am very interested in building a puzzle box. I have been looking at the page but really there are no instructions. I can order all the parts but need to know how to put them together. Is there any help you could give me?
    Thank you,

  5. Randy Wilkinson

    12 years ago

    How can I get a reverse geocache puzzle box? Can I order one, or is there some place that I can track one down now? This is a fantastic addition to an already wonderful activty. Thank you for your effort!

  6. Mikal

    12 years ago


    I should be posting some instructions on how to build a very basic puzzle box in the next few weeks.


  7. Chris

    12 years ago

    Hi Mikal,

    Have you posted anything on how to build a reverse geocaching box? If so could you send me the link.

    Thank you,

  8. Troy

    12 years ago

    I am thinking about making one for a proposal, how small of a range do you think you could have for the destination. 2000 meters just seems a little large and would like to try like 100 meters if that would work.


  9. Mikal

    12 years ago

    Troy, in my customizable boxes I find that radii of as little as 10-15 meters work fine. I can define the magic spot where the box opens at the front door of a shop, and not at the shop next door. The EM-406A GPS unit that I use has a published accuracy of +/-10 meters.

    You’d only use a radius like 2000 meters if you wanted, as I did, the box to open anywhere within a designated region, like on my island.


  10. Reina

    12 years ago

    I love your Reverse Geocache puzzle! I am looking for someone to make one for me. Any ideas of who would be willing to do it?

  11. Mikal

    12 years ago

    @Reina — Sure, send me an email.

  12. Kraig

    12 years ago

    Mikal, I am in the process of obtaining all the hardware to make one of these for my wife for our ten year wedding anniversary.
    As far as the LCD goes, is there a reason I would want more than the 8×2 LCD? If I wanted to have a message longer than eight characters will it just scroll across?


  13. Mikal

    12 years ago


    I love that little 8×2 display because it’s such a vibrant blue and because it is so small. There’s an aesthetic with these boxes that compels you to make the visible electronics as tiny as possible relative to the rest of the construction. That increases the impression that the strange object you have is a found artifact–which is good!

    That said, a bigger display would work. But there is no automatic scrolling. The boxes I make do have “fly-in” and “fly-out” messages, but this is custom code.


  14. Kraig

    12 years ago

    Mikal, thanks for the reply.
    I am having difficulty finding an illuminated push-button.
    The link you provided states “product not found”
    Do you have another source for one?

  15. Kraig

    12 years ago

    Mikal, never-mind about the switch, I found you link on building and thanks for all the info.

  16. david

    12 years ago

    Hi there Mikal,
    Thanks for the tutorial in Make magazine. I’ve just emailed you about a shield for this project, but leading on from the question about LCD’s. I’m trying to source the components within the UK and can’t seem to locate a suitable 8 x 2, but can find a 16 x 2 in a similar blue ( Should this work with your code?

  17. Mikal

    12 years ago

    @David, I would guess that that display would work ok, though you might have to work out the backlight issues on your own. (Backlighting resistors and techniques seems to be where these displays vary the most.)

    But the main issue is that the 8×2 connector on the shield is designed to perfectly mate with that cute little 8×2 display with a simple ribbon cable. If you use a 16×2 display, you’ll have to manually wire it up. But it will probably work.


  18. Jamie

    12 years ago

    Hey Mikal,

    First of all, congratulations on an absolutely awesome project. I’ve heard rumours that you are posting instructions on how to make your own box online? Has there been any progress on this? I’d love to make one for my best mate who is leaving us to travel overseas – thought it’d be a great way to get her to explore her new home :)



  19. Mikal

    12 years ago

  20. Joseph

    12 years ago

    I was wondering how I could go about getting a reverse geocache puzzle box built. I notice in one post you told the person to e-mail you but I couldn’t find your e-mail.

  21. Mikal

    12 years ago

    Hi Joseph…

    For commissioned work, contact me at mikal (at)


  22. Alban

    12 years ago

    speechless…. What a nice concept!!!!! Love it!!!

  23. Skippy

    12 years ago

    Where did you get that pushbutton switch? What did it cost?


  24. Mikal

    12 years ago

    Skippy, I link all the parts on the build page.

    Good luck!


  25. Marc

    12 years ago

    would you sell a few? I would like to create a game among my friends throughout the world to bring us all to one location at one time! my email is Please send a response either way. Thank you

  26. Mikal

    12 years ago

    Check your email, Marc!

  27. Alex

    12 years ago

    Hi Mikal,

    Thank you for such an excellent idea. I decided to make one for my (now) parents-in-law as a thank you for helping my (now) wife and me for our wedding. This was in the days before you posted the basic instructions (and published the code >_< ) so I was starting from scratch with just your description and photos to examine. Man, it was a lot of fun and it took over my dining room table for most of a month. It successfully opened for them last Thursday and they really enjoyed the idea and the hunt.

    I pretty much copied your design, but came across a few bits that might be useful for others going down this path:
    I wanted to set a tight tolerance (~ 10m) on the location so that they had to be standing right outside a particular B&B doorway before the box opened. Since they were taking their initial triangulation readings from a few 100km distant and it wasn't convenient to perform triangulations while on the road, I put in an extra function to counter the initial inaccuracies of triangulating over a large distance. Once they got within a couple of km of target, the box additionally gave them a direction to head in e.g. North West, South etc. This was 5 minutes' worth of coding and uses a pretty basic equation.
    I built the box in Australia and had to take it with me to the UK fully assembled. Seeing your concerns over flight safety, I got in touch with Qantas security before flying. The general message was not to worry about it. Security staff aren't stupid and provided there are no large masses within the box, they're pretty used to spotting hobby electronics on x-ray. If you're worried about it, mention it to check-in staff and make sure it's well-labelled in your suitcase. My bag didn't even get opened for inspection.

    Thanks once again for such a brilliant concept. It's given me and my new family a lot of fun, although wife will lament the loss of the dining room table.

  28. Dave

    12 years ago

    Would you be interested in building one of these devices for sale? I am interested in purchasing one but am not savy enough to build it. If so, it would be greatly appreciated. Feel free to send me an email. Thanks.

  29. Mikal

    12 years ago


    Thanks so much for terrific message. I think my favorite part of all this are the cool stories that are generated by other people. Can you share some more detail? Like what was in the box? A gift certificate for the B+B? What town? Can you share the name of the B+B?

    I have a fellow working on a box which will take his daughter to a beautiful rural park where she’ll find her extended family at a surprise cookout and a shiny new car! Can you guess what was in the box? Yep, you got it. A set of keys to the car!

    At some point I would like to better understand your comment about “the inaccuracies of triangulating over a large distance” and how you correct for this.

    Thanks again for the kind message; it made my day!

  30. Mikal

    12 years ago

    Check your email, Dave.


  31. BEN

    12 years ago

    Hi, this is one of the coolest things I’ve ever seen! It is such an awesome idea, and it’s great to see some creativity in this world haha! I saw you instruction link, but I was also wondering about just purchasing one; I did see where you told people to check their e-mails regarding purchasing one, so if you could, please send me an e-mail regarding buying one. Thanks!!!!

  32. Dave

    12 years ago

    Hey Mikal

    Interestingly, I am in the same situation as the other Dave. I would love to have one of these boxes, as I am preparing to ask the love of my life to marry me. However, as with the last Dave, building my own is not an option as I lack the intellect. This box is perfect!! PLEASE e-mail me with any help you can provide.

  33. Eric

    12 years ago

    I loved this idea when I saw it in MAKE, and hope to build one… someday.

    I’m sure you get suggestions all the time, but have you considered a “Brigadoon Box?” (I just made that up; I have no claim to that name). This would be a box like your original reverse geocache, but with the added element of time. The Brigadoon Box would only open at a certain place, ON A CERTAIN DATE (or ever a certain time). Like, say, Stonehenge at the summer solstice. New Years, midnight, Times Square. Sunrise, Christmas morning, grandma’s house.
    You could get the time/date information from the GPS module you already have, so you probably wouldn’t need to change your hardware. Just a few dozen more lines of code. (Easy for ME to say!)

    Anyway – might be fun to try.

  34. Mikal

    11 years ago


    I agree that’s a good idea, Eric. My new firmware will support the ability to set both (or either!) a destination OR a time for opening. You could create a box that only opens when your grandbaby’s 21st birthday.

  35. fedor

    11 years ago

    mikal, I would like to buy at least one… is it possible?

  36. Karl

    11 years ago

    HI, I was just wondering if you sell these. I would love to get one! Thank you, Karl

  37. Spencer

    11 years ago

    I really like this idea. I am glad I found this on the internet, this was well worth reading. I was actually considering making a box similar to this, and you have impressed me enough with this that I am motivated now. amazing.

  38. Adam

    11 years ago

    Is there any where to buy a reverse geocache box like this? I know a lot of people have been asking, but I can’t see to find any place. My gf and I love geocaching and I figure it’d be the best way to propose. Thanks for your help! :)

  39. Mikal

    11 years ago


    Yes, I am making several of these each month for various people. Let’s talk via email…


  40. Mark

    11 years ago

    Mikal, GREAT idea! I would love to have one of these, but there’s no way I could make it myself. Could you e-mail and let me know if you’d be willing to sell me one?


  41. wendy

    11 years ago

    Okay my question is very simple. CAN I BUY ONE OF THESE BOXES :) PLEASE ?

  42. Mikal

    11 years ago


    Sure! Check your email. I make lots of them.


  43. Mikal

    11 years ago


    Simple answer too: yes! :) I’ve made lots of commissioned boxes. We’ll talk by email. Thanks.


  44. Cesaera Pirrone

    11 years ago

    please let me know what one of these would cost – I am getting Married in August and would love to present my husband with one – now I must think about the contents – and a location..

    Thank you Cesaera Pirrone

  45. Jacq

    11 years ago

    Hi Mikal,
    3 words. I LOVE YOU!
    Can i buy one for my husband for our anniversary in May 2012?
    He has done some personal projects using the Arduino and we’ve recently got into geocaching together.
    I would have a go at building one but it is beyond me if im honest.

  46. Mikal

    11 years ago

    @Jacq–I love you too! :) Thanks for the kind note!
    @Cesaera–Thank you too!

    Yes, I am building commissions regularly, check your email for details!

  47. Bernard Martin

    11 years ago

    Hi Mikal
    I love your idea of making your own reverse geocache. I have some questions on making my own. Can you get in touch with me through my email address?? Thanks a lot.

  48. Tyler

    11 years ago

    This one of the most genius and creative gifts I have ever seen! How much does something like this cost? Would I have to send the contents of the box to you?

  49. Mikal

    11 years ago

    Bernard, did you see my page on building your own at

  50. Mikal

    11 years ago


    Thanks for the kind words. I have made many custom boxes from about $550 to upwards of $3000 depending on the level of customization required. My boxes are all configurable from a PC. You don’t send me the contents; you put the contents in the box and then select your destination on the PC console using some configuration software that I wrote. The software controls all aspects of the box, so you can have as many adventures as you like.

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  1. Tweets that mention The Reverse Geocache Puzzle | Arduiniana --

    [...] This post was mentioned on Twitter by Miles Burton, rethinker_news. rethinker_news said: [...]

  2. Reverse geocache puzzle - Hack a Day

    [...] gift for his friend who was moving to France. After experimenting with a few things, he settled on creating a puzzle box that would only open in a certain location. Since his friend introduced him to the Arduino, he fittingly used one in the design, along with a [...]

  3. Sobre Tecnologia » Blog Archive » Geocaching inverso

    [...] puzzle de geocaching inverso es realmente ingenioso: lo creó Mikal utilizando Arduino, y básicamente consiste en una caja [...]

  4. Reverse Geocache Puzzle doles out presents depending on location - SlashGear

    [...] just what Mikal did for the friend who introduced him to Arduino tinkering.  He constructed the Reverse Geocache Puzzle, a wooden box that would only be unlocked when within 2km of a location Mikal preprogrammed into [...]

  5. uberVU - social comments

    Social comments and analytics for this post…

    This post was mentioned on Twitter by TeamMCS: Great #Arduino project/gift…

  6. Charles Rincheval (hugokernel) 's status on Monday, 19-Oct-09 15:12:12 UTC -

    [...] le bon endroit et la boite s’ouvrera #geocache #arduino #gps [...]

  7. Twitted by Hardwarer

    [...] This post was Twitted by Hardwarer [...]

  8. GPS Puzzle Box Only Opens In One Specific Location [GPS] | dv8-designs

    [...] a servo, and a GPS. I guess the puzzle itself is present enough, really. Pretty cool stuff, no? [Arduiniana via [...]

  9. An amazing gift «

    [...] This might not be the finest crafted of gifts, but the concept and thought behind it are wonderful. It is a gift box that only opens at a certain location. A kind of reverse-geocache. Read the full story behind it and details of its creation here. [...]

  10. Geocaching inverso

    [...] Geocaching por pcmaster hace pocos segundos [...]

  11. GPS Hunt Project - Hacked Gadgets - DIY Tech Blog

    [...] GPS Hunt Project is very interesting, the box is electronically locked and the only way to open it (without using [...]

  12. Status-Q » Blog Archive » Think outside the box to get inside the box

    [...] a wonderful hardware project, very nicely written up by Mikal Hart. Possibly-related posts:Drop it in the box I’ve only [...]

  13. Twitted by darkbalder

    [...] This post was Twitted by darkbalder [...]

  14. telemekus's status on Tuesday, 20-Oct-09 09:17:50 UTC -

    [...] like to Geo cache? This is pretty cool. Reverse Geo Caching puzzle. [...]

  15. GPS Hunt Project | Gadget Warezhouse

    [...] This GPS Hunt Project is very interesting, the box is electronically locked and the only way to open it [...]

  16. GPS Puzzle Box makes you follow directions before it opens » Coolest Gadgets

    [...] It is actually a really cool idea if you or someone you know loves to solve puzzles and mysteries.  Then not only could you give them a cool gift, but you could make sure they’ve worked hard to get their hands onto it.  The box was originally built by Makal Hart as a wedding gift.  On the top it features a button and an LCD display.  You can only press the button 50 times, but every time you do it’ll tell you how many kilometers you’re away from the spot you need to be at.  You can check out a more detailed look on the box from the creator’s perspective by going here. [...]

  17. Homemade GPS puzzle box puts a modern spin on treasure hunts | Netbook Gizmo

    [...] Read | Permalink | Email this | Comments [...]

  18. caja-puzzle

    [...] arduiniana Compartir Si te gustó este post, agrega tec.nologia a tu lector RSS | 0 comentarios Por tecnologia tec.nologia Tags cajas, cajas puzzle, gps, puzzles October 21st, 2009 @ 4:46 am [...]

  19. » La Caja de Regalo Más Geek: Una

    [...] Arduino y fué creado por Mikal, El funcionamiento es sencillo: Es una caja que tiene un sistema de GPS que sólo se puede abrir si [...]

  20. gift ideas by the stars » Blog Archive » Finding this wedding gift was quite a trip

    [...] what’s in the box with the GPS screen? Gift cards. Mikal has been getting inundated with orders to make more of these one-off boxes which took him nine months to [...]

  21. The Reverse Geocache Puzzle – GPS In a Box | GPS Crunch

    [...] Geocache Puzzle. A device based on a simple concept that is getting a lot of coverage these days. Mikal Hart has certainly developed an interesting GPS box. A box that will tell you where it will open but [...]

  22. Homo Sum » Blog Archive » Aside: Magic Boxes

    [...] have two immediate reactions to a story about someone constructing a box that will only open at specific coordinates as a wedding gift. First, I am forced to wonder why I have never been given such a thing–my [...]

  23. Gadgets » Blog Archive » Geocaching umgekehrt

    [...] Bastler Mikal Hart drehte dieses Konzept um und konstruierte für einen alten Freund als Hochzeitsgeschenk eine [...]

  24. Pasta&Vinegar » Blog Archive » Playulf09 write-up

    [...] The Reverse Geocache Puzzle by Mikal Hart which is a puzzle box that only opens up at specific locations [...]

  25. El regalo geek ideal | Saturn Attacks

    [...] esto es lo que se le ocurrió al buen Mikal Hart — The Reverse Geocache Puzzle — para la boda de un buen amigo suyo y a quien en verdad [...]

  26. Nouvelles technologies: Geocaching inversé

    [...] Ce puzzle de geocaching inversé est réellement ingénieux : Mikal l’a créé en utilisant Arduino, et il consiste basiquement en boîte j’offre (des mariages) qui pouvait seulement être ouvert quand il était physiquement situé dans un lieu concret du monde. Dans son intérieur il y avait un GPS qui contrôlait un mécanisme qui bloquait la serrure, qui serait seulement ouverte après être arrivé aux coordonnées correctes, nourri par une batterie. À travers d’un écran, et après une pulsation, il indiquait pendant trois minutes la distance à l’objectif. Tout un cadeau geek avec un style, terriblement ingénieux et amusé pour les amants des puzzles. § Hack-a-day. # Un lien Permanent Posted by lisa conley at 10:41 AM [...]

  27. Technology society: Umgekehrter Geocaching

    [...] Dieses Puzzle von umgekehrtem Geocaching ist wirklich sinnreich: Es hat Mikal geschaffen, Arduino benutzend, und hauptsächlich besteht es in einer Kiste ich schenke (von Heiraten), der nur geöffnet sein konnte, wenn er in einem konkreten Ort der Welt physisch gelegen war. In seinem Innenraum gab es einen GPS, der einen Mechanismus kontrollierte, der das Schloss blockierte, das nur ernährt von einer Batterie geöffnet werden würde, nachdem er zu den fehlerfreien Koordinaten kommen würde. Über einen Schirm zeigte er die Entfernung und nach einem Pulsschlag, während drei Minuten im Ziel an. Das ganze Geschenk geek mit Stil, fürchterlich sinnreichem und unterhaltenem für die Liebhaber der Puzzles. § Hack-A-Day. # Bleibende Verbindung Posted by Lupe Mura at 9:50 AM [...]

  28. Learning technology: Обратный Geocaching

    [...] Эта головоломка обратного geocaching действительно изобретательная: это создал Mikal используя Arduino, и главным образом он состоит из ящика я дарю (свадеб), что только мог быть открытым, когда он был физически расположенным в конкретном месте мира. В его внутреннем помещении был GPS, который контролировал механизм, который блокировал замок, который только открылся бы, прибыв в правильные координаты, питаемый батареей. Через экран, и вслед за пульсацией, он показывал в течение трех минут дистанцию в цель. Целый подарок geek со стилем, ужасно изобретательным и развлеченным для любовников головоломок. § Hack-a-day. # Постоянное соединение Posted by Lupe Mura at 4:10 PM [...]

  29. EPISODE 126 – Midwest Meet Up Cacher Coffee « Goecaching Podcast

    [...] LogTools for making Garmin custom raster mapsReverse Geocaching PuzzleState Parks permit sales up [...]

  30. Homemade Geocache Puzzle Box — The Gadgeteer

    [...] good friend David Simpson sent me an email tonight with a link to a really cool story. I love a good story and I love a good gadget. Make it a 3 part story about [...]

  31. DIY Reverse Geocache Puzzle | Must Have Gadgets

    [...] you don’t see everyday, a DIY reverse geocache puzzle box, given as a wedding gift. Using the Arduino prototyping platform and a GPS device, it will lead you to a specific location on the globe, before [...]

  32. The Reverse Geocache Puzzle «

    [...] [...]

  33. Buzzle – Morse Code based Puzzle

    [...] was checking out the new posts on when I bumped into The Reverse Geocache Puzzle™ made by Mikal [...]

  34. The Frustromantic Box, Part 1: Intro « New Bright Idea

    [...] Frustromantic Box, Part 1 A few months ago, Hack A Day featured an ingenious hack called the Reverse Geocache Puzzle by a gentleman named Mikal Hart (please note that “Reverse Geocache Puzzle” is [...]

  35. The Frustromantic Box, Part 2: Assembly « New Bright Idea

    [...] Box, Part 2: Assembly The Frustromantic Box is my implementation of Mikal Hart’s Reverse Geocache Puzzle.  In Part 1 of this series I gave an overview of the project and its parts list.  This post [...]

  36. The Frustromantic Box, Part 3: Electronics « New Bright Idea

    [...] I had a real problem processing the output of the PNA4612 module when the batteries are even slightly discharged.  This might be something I could correct in software, but if I were doing it again, I’d probably just run a barrel jack through the side of the box, similar to what Mikal did on the original puzzle box. [...]

  37. Morse code puzzle box | Products & Tech News

    [...] box that can only be opened if a specific morse code sequence is entered. His starting point was a Reverse Geocache Puzzle he’d read about on Hack a Day, where a person has to bring a box to specific coordinates to release [...]

  38. Morse code puzzle box | SquareCows

    [...] box that can only be opened if a specific morse code sequence is entered. His starting point was a Reverse Geocache Puzzle he’d read about on Hack a Day, where a person has to bring a box to specific coordinates to [...]

  39. adoption curve dot net » Blog Archive » links for 2010-02-18

    [...] The Reverse Geocache Puzzle ™ | Arduiniana "The new couple, freshly back from their honeymoon, remove the wrapping to reveal a book-sized wooden box elaborately carved with elephant images. (I didn’t carve it; I bought it that way at World Market.) Mounted into the lid, perhaps incongruously, are an illuminated button, a small display, and a mysterious module that sharp-eyed readers might recognize as a GPS. There’s also some kind of connector tucked away on the box’s left side." (tags: arduino geocaching geodata location projects ideas) [...]

  40. Dorkbot 23 – SXSW Interactive 2010 « dorkbot-austin

    [...] Mikal Hart – Reverse Geocache box [...]

  41. My first (completed) project! « Stromberg Labs

    [...] couple months ago I saw this awesome project and realized that I had a couple of the parts already, so it got into my head that I could build [...]

  42. Reveling in dorkery – tales from SXSW #1 | Rubber Republic

    [...] up was a guy called Mikal Hart who’s invented the “Reverse Geocache box“.  I expect you know what one of these is – but if you don’t the shortened [...]

  43. صندوق الأحجية المتصل بالقمر الصناعي: كان يُقدم في البداية كهدية زفاف… « Endoacustica Arabic Blog

    [...] الصندوق المتصل بالقمر الصناعي عبارة عن قطعة خشبية من النوع الذي من الممكن أن تجده [...]

  44. Introduction | Jordan LeGrand's Arduino Journey

    [...] inspiration from Mikal Hart’s Reverse Geocache Puzzle, I wil be constructing a gps scavenger hunt. Upon completion, the box will be locked from the [...]

  45. Little Reverse GeoCache - Markus’ Blog

    [...] Markus on Jun.19, 2010, under Electronics A few months ago I stumbled across the very first Reverse GeoCache project by Mikal Hart. I was fascinated by the idea and decided to build one of my [...]

  46. Smallest reverse geocache puzzle yet | Komprol

    [...] latest version of Mikal Hart’s original reverse geocache puzzle–a box that only opens in one location on the Earth’s surface–is by Markus. At [...]

  47. GPS Box Project - Opens at secret location - Hacked Gadgets - DIY Tech Blog

    [...] featured before. Markus has made a project he calls the Little Reverse GeoCache, it is based on a similar project that was made by Mikal Hart. The box can only be opened when it is in the correct location, the trick is that the location is [...]

  48. Caja Fuerte con GPS

    [...] El proyecto es un DIY por lo que podemos, si tenemos las ganas y los conocimientos llevarlo a cabo y no se ustedes, pero lo primero que me viene a la mente es por ejemplo: Una propuesta de matrimonio muy original con un estilo diferente. [...]

  49. GPS Box Project – Opens at secret location |

    [...] featured before. Markus has made a project he calls the Little Reverse GeoCache, it is based on a similar project that was made by Mikal Hart. The box can only be opened when it is in the correct location, the trick is that the location is [...]

  50. Blog ETBnetco » Caja Fuerte con GPS

    [...] proyecto es un DIY por lo que podemos -si tenemos las ganas y los conocimientos llevarlo a cabo- animarnos a hacer [...]

  51. “Special” Caches « GeoCass UK GeoCaching

    [...] doesn’t support so I will just ignore them), Cache In Trash Out, and the locationless “Reverse Caches” which sound mega exciting, but I don’t believe we have any in the UK. Reverse caches [...]

  52. Kristians lille hjørne på verdensveven » Reverse Geocache del1

    [...] A Day en artikkel om en fyr som hadde laget en reverse geocache. Dere kan lese om hele prosjektet her. I bunn og grunn så er prinsippet at man får en boks som er programmert med en fast geo-lokasjon. [...]

  53. Reverse geocache puzzle « at0mic blog

    [...] gift for his friend who was moving to France. After experimenting with a few things, he settled on creating a puzzle box that would only open in a certain location. Since his friend introduced him to the Arduino, he fittingly used one in the design, along with a [...]

  54. Un regalo ingenioso y original a la vez

    [...] Mikal Hart usando el sistema Arduino. Puedes encontrar toda la información sobre este proyecto en: The Reverse Geocache Puzzle. También puedes encontrar más información en microsiervos. Arduino, batería, caja de [...]

  55. GPS Puzzle Box Popularity |

    [...] featured a cool GPS Puzzle Box earlier this year that Markus built. It was based on a version that Mikal Hart created. Turns out there is quite a bit of interest in these GPS Puzzle Boxes, Mikal has since written a [...]

  56. GPS Puzzle Box Popularity | new technology, latest technology, robonaut, pc technology, latest business technology, technology in business, technology innovation, information technology, emerging technology

    [...] featured a cool GPS Puzzle Box earlier this year that Markus built. It was based on a version that Mikal Hart created. Turns out there is quite a bit of interest in these GPS Puzzle Boxes, Mikal has since written a [...]

  57. The Reverse Geocache Puzzle « Yeah Totally

    [...] Leave a Comment via [...]

  58. The Reverse Geocache Puzzle | myninjaplease

    [...]> Share this: [...]

  59. London to host Internet Week « V E X E D

    [...] last night New EC2 Features: Tagging, Idempotency, Filtering, Bring Your Own Keys JDK 7 Features The Reverse Geocache Puzzle Box Everyday at Vexed we round up the industry stories that we find interesting and insightful. These [...]

  60. Tuesday various « occasional fish

    [...] The Reverse Geocache Puzzle Box [via] [...]

  61. Self-Aware Building Blocks « Reputation Research Blog – Ben Turner

    [...] unlock a secret temple.  After all, one inventor using Arduino and GPS geolocation already made a wedding gift puzzle box that only opens when it’s taken to a small island near [...]

  62. Stubborn Treasure Chest | Rolang's Creeping Doom

    [...] was inspired by a real product, that uses a GPS-based lock that will only open in one location on earth. Be sure to read the [...]

  63. Il puzzle… fisico! Genio & follia «

    [...] questo The Reverse Geocache™ Puzzle Box e poi il seguito: cinque settimane dopo, le riflessioni su questo mondo di guardoni e finalmente [...]

  64. CacheDuino – Part 1 « Steve's Projects

    [...] my Mikal Harts “Reverse Geocache Puzzle” and Russ Weeks “Frustromantic Box” I thought I’d try build my own and use [...]

  65. Thomas Kalil, White House Office of Science and Technology Policy, talks Maker Movement | Live Sock

    [...] engineer who had the inspired idea to use reverse geocaching to design a wedding present — a puzzle box that only opens on one spot on the [...]

  66. New Arduino boards make electronics prototyping even easier « HackColorado Blog

    [...] and programming. Tons of cool projects have been created with the Arduino, including the Reverse Geocache Puzzle, high altitude balloons, and even lift status displays for Copper Mountain Resort. The new Arduino [...]

  67. Hidden Distance » Reverse Geocaching

    [...] Idee! Zur Bastelanleitung… Permalink — Kategorie: Randnotiz · Worthwhile — Hirschi @ 6:55 — [...]

  68. Reversing all the way to France « Lavonardo

    [...] wedding gifts go, this reverse geocache ranks amongst the finest. Filed under geocaching Comment (RSS) [...]

  69. World’s Strangest | Reverse Geocache Puzzle Box

    [...] Link | Part 2 of the story – via Gizmodo [...]

  70. The Reverse Geocache™ Puzzle Box « Verbasterd

    [...] A puzzle box that won’t open until it is taken to a certain location. Bron: Arduiniana [...]

  71. Yesterday

    [...] [...]

  72. Geolinkdump GPS, geocaching week 46

    [...] over de Reverse Geocache Puzzle Box. Erg mooi uitgevoerde ‘omgekeerde’ geocache die alleen open gaat op een vooraf [...]

  73. Connect Phi-1 shield with an EM 406A GPS « Liudr's Blog

    [...] you thought of making a fun Geocache box for outdoor adventure or a wonderful reverse-Geocache box for friends or loved ones? Maybe you want a GPS tracker for field trips or position-sensitive [...]

  74. Fully functional Arduino GPS logger « Liudr's Blog

    [...] exist endless ways that you can use a GPS sensor in your projects. Geocaching and reverse geocaching are just two typical applications. Last time I made an attempt to use GPS with Arduino and my Phi-1 [...]

  75. Reverse Geocache | Alternet

    [...] project was inspired by the “Reverse Geocache Puzzle Box“, an idea that has been duplicated a few times.  For Christmas this year, I drew my [...]

  76. Mikal Built a Magical Box :: CultureBy – Grant McCracken

    [...] Mikal. n.d. “The Reverse Geocache™ Puzzle Box.” Arduiniana. (Accessed October 4, 2010). Categories : [...]

  77. LlamaByte | Ramblings of a man named Bill

    [...] had read The Reverse Geocache Puzzle story awhile back and thought it was a fantastic idea. As I was thinking about a creative way to [...]

  78. Finding this wedding gift was quite a trip | It's In The Stars

    [...] what’s in the box with the GPS screen? Gift cards. Mikal has been getting inundated with orders to make more of these one-off boxes which took him nine months to [...]

  79. Arduino – Maximum and Minimum Temperature

    [...] PS: I know these last few posts aren’t about Geocaching, but bear with me. I am learning this stuff so I can create my own version of the Reverse Geocache… [...]

  80. Puzzle Box – The Paleotechnologist

    [...] since reading about the (original) Reverse Geocache a few months ago, I had wanted to build one. Except for the box itself, I already had all of the [...]

  81. Physical Computing | maplemuse

    [...] interesting examples of physical computing change the way we interact with technology. Take the GPS locked treasure box, which will only unlock at particular coordinates, telling the user how far away the correct [...]

  82. Reverse Geocaching | worms wiggle

    [...] not know about, and I stumbled upon something called reverse geocaching. You can read about it in Mikal Hart’s post (recommended). Basically, The idea is that you give someone a locked gift box, that they cannot [...]

  83. Interessante Arduino-Setups | wer bastelt mit

    [...] the-reverse-geo-cache-puzzle und [...]

  84. OSCON 2011 « Ted Leung on the Air

    [...] makes it possible for these people to make smart craft items. Some examples of such items are this “reverse geocache” wedding gift box, and a bicycling jacket with turn signal lights embedded in [...]

  85. Self-Aware Building Blocks « Ben Turner's Blog

    [...] unlock a secret temple.  After all, one inventor using Arduino and GPS geolocation already made a wedding gift puzzle box that only opens when it's taken to a small island near [...]

  86. Moments « Ben Turner's Blog

    [...] even the story about the wedding gift a man made for his newlywed friends which consisted of a locked box that had a butt….  The box said the newlywed couple would have 50 presses of the button to figure out how to open [...]

  87. Link Dumpage for 2010-05-25 | b2c8b8

    [...] The Reverse Geocache Puzzle ? | Arduiniana Delicious tags: puzzles "I finally settled on building the device I describe here: a puzzle box that won?t open until it is taken to a certain location … Mounted into the lid, perhaps incongruously, are an illuminated button, a small display, and a mysterious module that sharp-eyed readers might recognize as a GPS." [...]

  88. Dosenfischen: Geocaching-Podcast 195 › Geocaching-Podcast Dosenfischer

    [...] * Reverse Geocaching – Noch so ein talentierter Bastler, der hier Boxen für Reverse Geocaching vorstellt. Weitere Infos zum Thema gibts auch auf dieser Seite. [...]

  89. My Proposal Box, Part 1: Intro

    [...] seeing a project from Mikal Hart called The Reverse GeoCache™ Puzzle Box, I knew that I had to build one. My girlfriend and I really enjoy geocaching together, so I [...]

  90.’s top ten arduino projects - DIYourfaceoff | DIYourfaceoff

    [...] Check out the full write-up and build here [...]

  91. Puzzle Box |

    [...] stumbled across a link some time ago that showed how Mikal Hart built a Reverse Geocache(TM) as a wedding gift using an Arduino, a GPS, a small LCD display and a servo to drive the lock. For [...]

  92. Puzzle Box Part 2 |

    [...] Hart’s original Reverse Geocache Puzzle (TM) and More Puzzle Box Tales on his [...]

  93. Valentine’s day puzzle box « Matt's Hacks

    [...] I didn’t really have a specific project in mind for a while.  Then, one day I remembered a reverse geocache box that was also featured on hackaday, and realized that I could do something similar.  The F3 [...]

  94. Phul's Phantasmagorium

    [...] the other day I read about the “Reverse Geocache” project  ( and it gelled a rather important concept for me.  It was an example of something that has been [...]

  95. The Traveling Geocache using Arduino - Arduino for ProjectsArduino for Projects

    [...] The original reverse geocache: [...]

  96. Finding my creative spark - Geocaching Librarian

    [...] for the Arduino which let you create some amazing projects. A couple of examples that I found are a reverse geocache, and The Inebriator. Both of these are well outside my skill level at the moment, but hopefully [...]

  97. Reverse Geocaching Wedding Gift Box |

    [...] A while ago, friends of mine got married. Like so often, we tried to come up with some extraordinary cool wedding present. They both enjoy hiking and geo-caching, which inspired us to make the following present. We found an awesome idea online, the reverse geo-caching puzzle. The original description can be found here: [...]

  98. bildr » Finding Location With The EM-406A GPS + Arduino

    [...] this that will return the value in miles, nautical miles, or kilometers. You can use this to create reverse geo-caching gifts or have it trigger something every X [...]

  99. MindTribe | Geeky Romantic Suggestions

    [...] can also combine gifts. The perfect customized or handmade item could fit inside a reverse geocache box which leads your beloved to the location where you’ll be serving your awesome home-cooked [...]

  100. » Der umgekehrte Geocache

    [...] Tüftler Mikal Hart hat das Spiel nun einmal etwas anders aufgezogen bzw. [...]

  101. Reverse GeoCaching | Huinink-Jongen

    [...] link – Arduiniana – de uitvinder van….  YouTube [...]

  102. CS 436 Lecture ? – O Marks The Spot | teaching machines

    [...] app we’ll write today is inspired by the Reverse Geocache Puzzle. Intel software engineer Mikal Hart had a friend who was getting married. This friend had [...]

  103. Reverse geocaching: bouw zelf zo'n box met Arduino - Mancave

    [...] je kan ook middels coördinaten de box laten openen. Zoals Mikal Hart laat doen. Hij heeft er een coördinaat ingestopt en pas als je daar in de buurt bent, kan je de [...]

  104. GPS Puzzle Box makes you follow directions before it opens | Coolest Gadgets

    [...] It is actually a really cool idea if you or someone you know loves to solve puzzles and mysteries.  Then not only could you give them a cool gift, but you could make sure they’ve worked hard to get their hands onto it.  The box was originally built by Makal Hart as a wedding gift.  On the top it features a button and an LCD display.  You can only press the button 50 times, but every time you do it’ll tell you how many kilometers you’re away from the spot you need to be at.  You can check out a more detailed look on the box from the creator’s perspective by going here. [...]

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