Geocache Locator Is The Gift That Keeps On Giving

Depending on how you look at things, the holidays could be seen as either an excuse to spend money or an excuse to get creative. We imagine many Hackaday readers would rather head to their workbench than the mall when it comes time for gift giving, and [Sean Hodgins] is no different. He came up with the idea of hiding geocaches around his nephew’s neighborhood and building him a locator device to find them. The locator itself is intended to grow with his nephew, allowing him to reprogram it or use its parts for something completely different down the road.

The main components tucked inside of the 3D printed case of the locator are an Adafruit Trinket, a GPS receiver, and a compass module. The Adafruit NeoPixel Ring is of course front and center, serving as the device’s display. To power the device there’s an old battery, a LiPo charger circuit, and a 5V converter.

One of the goals for the project was that it could be constructed out of things [Sean] already had laying around, so some concessions had to be made. The Trinket ended up having too few pins, the compass lacks an accelerometer, and the switches and buttons are a bit clunky for the build. But in the end it comes together well enough to get the job done, and at least he was able to clear some stuff out of his parts bins.

To allow its owner to disassemble and potentially rebuild it into something else later, no soldered joints were used in the construction of the locator. Everything is done with jumper wires, which lead to some interesting problem solving such as using a strip of pin header as a bus bar of sorts. A bit of heat shrink over the bundle holds everything together and prevents shorts.

Location-aware gadgets happen to be an extremely popular gift choice among the hacker crowd. We’ve covered everything from devices cobbled together from trash to hardware which could pass for a commercial product.

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Snail Is Actually Cleverly Strange Geocaching Waypoint

Basic geocaching consists of following GPS coordinates to a location, then finding a container which is concealed somewhere nearby. Like any activity, people tend to add their own twists to keep things interesting. [Jangeox] recently posted a video of the OLED Snail 2.0 to show off his most recent work. (This is a refinement of an earlier version, which he describes in a blog post.)

Another of [Jangeox]’s Electronic Waypoints
[Jangeox] spices up geocaching by creating electronic waypoints, and the OLED Snail is one of these. Instead of GPS coordinates sending someone directly to a goal, a person instead finds a waypoint that reveals another set of coordinates and these waypoints are followed like a trail of breadcrumbs.

A typical waypoint is an ATTINY85 microcontroller programmed to display an animated message on the OLED, and the message reveals the coordinates to the next waypoint. The waypoint is always cleverly hidden, and in the case of the OLED Snail 2.0 the enclosure is the shell of a large snail containing the electronics encased in resin. This means that the devices have a finite lifespan — the battery sealed inside is all the power the device gets. Fortunately, with the help of a tilt switch the electronics can remain dormant until someone picks it up to start the show. Other waypoints have included a fake plant, and the fake bolt shown here. Video of the OLED Snail 2.0 is embedded below.

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Hack Your Hike With This Arduino Puzzle Geocache

For those who love to hike, no excuse is needed to hit the woods. Other folks, though, need a little coaxing to get into the great outdoors, which is where geocaching comes in: hide something in the woods, post clues to its location online, and they will come. The puzzle is the attraction, and doubly so for this geocache with an Arduino-powered game of Hangman that needs to be solved before the cache is unlocked.

The actual contents of a geocache are rarely the point — after all, it’s the journey, not the destination. But [cliptwings]’ destination is likely to be a real crowd pleaser. Like many geocaches, this one is built into a waterproof plastic ammo can. Inside the can is another door that can only be unlocked by correctly solving a classic game of Hangman. The game itself may look familiar to long-time Hackaday readers, since we featured it back in 2009. Correctly solving the puzzle opens the inner chamber to reveal the geocaching goodness within.

Cleverly, [cliptwings] mounted the volt battery for the Arduino on top of the inner door so that cachers can replace a dead battery and play the game; strangely, the cache entry on (registration required) does not instruct players to bring a battery along.

It looks like the cache has already been found and solved once since being placed a few days ago in a park north of Tucson, Arizona. Other gadget caches we’ve featured include GPS-enabled reverse caches, and a puzzle cache that requires IR-vision to unlock.

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Myst(ery) Box

Anyone remember the game Myst? Well, [Michael] and his girlfriend have been playing quite a bit of it lately, so for her birthday, he decided to make her something inspired from it.

For those unaware of the classic that is the Myst series, it is a set of games that started back in 1993 where you assume the role of the Stranger who gets to explore other planets (called Ages) to solve various logical and mechanical puzzles.

Anyway, [Michael] got his girlfriend tickets to visit GC319QK (a geocache site requiring diving) — since the gift is a relatively small token, it was logical for [Michael] to make a fancy box for it — and that’s exactly what he did. It’s a peculiar little wooden box with LEDs, a button, a latch, an unplugged wire, different rods and strange looking sensors — and it is a very clever little puzzle.

We could explain to you how it works (with the Arduino, phototransistors and maybe the source code), but instead we think you’ll enjoy watching [Michael’s] video of it.

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Putting The Brains Of A Reverse Geocache On The Outside


A reverse geocache – a box that only opens in a specific geographical area – is a perennial favorite here at Hackaday. We see a ton of different implementations, but most of the time, the builds are reasonably similar. Of course dedicating a GPS receiver solely to a reverse geocache isn’t an inexpensive prospect, so [Eric] came up with a better solution. He’s using a smart phone as the brains of his geocache, allowing him to keep the GPS and display outside the locked box.

The build began by finding an old box and modifying it so it can be locked with a servo. The only other bits of electronics inside the box are an IOIO board, a battery pack, and an I2C EEPROM for storing a few settings. On the phone side of things, [Eric] wrote an Android app to serve as both the programming interface, UI, and GPS hardware for his reverse geocache. It’s exactly like all the other reverse geocaches we’ve seen, only this time the controls are wireless.

[Eric] put up a video demoing his reverse geocache. You can check that out after the break.

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Infrared Hides Code Combination On Geocache Puzzle

[AJ] and [Brian] are making sure the geocache challenges they set up take some ingenuity to solve. They’ve just rolled out a two-part cache which uses a code hidden in infrared light.  (Editor’s note from the far future: link wend dead.  Have a look in the Wayback Machine.)

The first part of the cache is a box (the black one on the left) which contains a mysterious hand crank and a smaller box that has a combination lock on it. The second stage is the wooden box on the right. It’s got a hole in the side to receive the hand crank. This connects to the dynamo inside, letting you build up some electricity as it spins. Inside the case you’ll see two red lights blink as the crank is turned, but when you push the button on the outside of the box nothing will happen. That is, unless you’re looking through a camera which can pick up infrared light. The code (710 in this case) is displayed in an array of IR LEDs, and is used to open that combination lock. We wonder if there’s any clues about using a camera or if you have to figure this out on your own.

Don’t miss the video after the break for a full demo of the system.

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Speech Recognition Geocache: Se Habla Español

Instructables user [jorgegunn] has put a unique spin on a recent geocache build by incorporating speech recognition and requiring that the “finder” knows the secret password to access the loot contained within. Although we won’t spoil the fun here, the techie spirit of the build was further bolstered by choosing a password fitting for any trekkie.

Despite utilizing an off-the-shelf speech recognition circuit kit, the majority of this hack was accomplished using parts available at local electronics and hardware stores. [jorgegunn] went to great lengths to make this hack accessible to any amateur hobbyist  and even includes links to relevant tutorials, schematics, and online parts vendors where applicable.

The actual speech recognition is accomplished with an Images Scientific Instruments model SR-06 circuit kit, capable of recognizing up to 40 different predefined words across multiple languages. Any time a correct match occurs, a value corresponding to the memory slot for that word is displayed on a pair of 7-segment displays. A separate decoder circuit based on a 74LS373 D-Type Latch and 4028 IC Decoder CMOS determines if the value being displayed constitutes a valid response and then drives a solenoid via a Darlington transistor in order to release the latching mechanism. Once opened, the device is simply pushed closed again to await its next finder- we are guessing that finding it might actually be the easiest part as judged by its size!

Although the real-world battery life has not yet been determined, a single coin cell for memory retention and a 9V battery used to drive the circuit and for latch release lasted through a full month of testing without any issues. Battery life could be extended almost indefinitely with a simple solar cell and rechargeable battery setup, but this would also obviously increase the likelihood of vandalism and/or theft.

We can imagine many different applications for such a device as-is including automated door lock  mechanisms and even access control to things such as the controls on a computer case.  It should also be fairly easy to increase the security by stringing multiple words together into a password or by instituting a “time out” period after a certain number of incorrect guesses.

Let us know of any other applications or build variations in the comments below and make sure to see how it all came together in the short videos after the break.

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