Creating a Gadget Cache for a Mega Event

Several months prior to the annual Berkshire GeoBash Mega Event in Massachusetts (USA), I was contacted to see if I’d be interested in creating a gadget cache for their event. I said “Yes!” of course. I never dreamed it would end up as a top-ten favorited cache in my state.

Don't Shock the Goat (GC6JZ0Q) Don't Shock the Goat (GC6JZ0Q)

Once I had accepted, the real pressure started.  What kind of cache to make?  I keep a list of future gadget caches I’d like to make, and started looking at it.  The “Wacky Wire” idea jumped out at me.  Most of the ideas I’ve had would fit in a birdhouse style form-factor, but I knew the Wacky Wire cache would need to be bigger.  Luckily, the mega event host, Bousquet Ski Resort, had no problem with that.

At first, I was going to use Signal the Frog as the theme, since he is the face of geocaching, and he does visit for the event. About a week later, I realized that I could use a goat instead.  A goat has been part of the theming for this mega event the past four years, so I jumped on that idea. I found a simple goat outline that they used in the second year, and based my cache around that.

Inspiration: Bershire GeoBash #2 Pathtag

Inspiration: Bershire GeoBash #2 Pathtag

The Result

The cache page is at Because it was launched a week prior to the mega event, a few locals were able to give it a shot before all the attendees. Geocacher bdubs213 was there within an hour after it was published, and recorded his FTF experience!

Video: FTF with bdubs213 and chicken34

The 3videosisters also visited soon after the cache came out and shot a video. They had the extra experience of herding up some animals on their way to the cache. Bousquet Ski Resort sometimes has an animal pen around the woods where this cache is kept – the animals chew back all the vines and invasive species. They are completely fine with people entering the pen to access the cache.

Video: 3videosisters Meet the Goat

There were a few more finds over that first week, and everything went great. It’s only my third gadget cache, so I was happy to see people enjoying the cache without any glitches.

Then the Mega hit. The cache does take a bit of time to open, and a line formed. There seemed to be at least a few people waiting their turn through most of the day. I was nervous the line may sour some people’s experience. Looking at the logs of the cache and event, no one seemed to mind, thankfully. Maybe because the cache was big enough for everyone to watch, it made it more interesting? There was a bit of pressure on each geocacher when it was their turn, since a bunch of people in line were watching.

Waiting in Line to Try "Don't Shock the Goat"

Waiting in Line to Try “Don’t Shock the Goat”

Many photos were taken, here are a few that geocachers shared with me:

By the end of the day, over two hundred people had logged the cache, and by the end of the week, GC6JZ0Q: Don’t Shock the Goat, was a top-ten favorited cache in Massachusetts. It is still very surreal to me.

That’s how the event went. To learn more about the cache and make your own, keep reading!

Building the Container

My wife has a Cricut paper cutter for her scrapbooking hobby, so I asked to use that to cut out some stencils. The stencil had to be big enough so I could bend a wire of decent thickness/stiffness and have a geocacher be able to move an eyebolt around it, so I decided to make the stencil as big as 4 sheets of paper taped together. I realized that this size would work well on a 2×2′ square of plywood, so all configurations would be based on that size.

I also figured the cache wouldn’t have to be very deep. I played around with some 2x4s, and though that would be deep enough. The battery holder, the latching mechanism, and the cache container would all fit in a 3.5″ deep space, so I decided to stay with the 2x4s for the primary supports. Using existing lumber sizes makes the build go quicker.

The whole thing ended up being 24x24x6″ – bigger than I had originally planned, but it worked out really well. Because it was at a Mega Event, there were always people around it. Being so big, it was easy for people nearby to see how others we doing.

Creating the Circuit

So the idea was pretty simple: one wire was the wand, one was the goat outline, one to start the game, and one to finish it. The wand itself would be the 5V lead, and the others were set to be digital input pins. I would test each of the inputs by touching the wand wire to them to see if they were being used to complete the circuit. It looked something like this (power supply not shown):

Circuit Test #1 - Do NOT do this

Circuit Test #1 – Do NOT do this

It didn’t work. The goat outline, start, and finish pins on the Arduino board would go off randomly, or not at all. I had no idea what was going on.  It was time to do some reading.

And then I come across pull-down and pull-up resistors.  I have never heard of such a thing before.  Apparently, you can’t just leave input pins unconnected, or the values “float”. I may write more about this later.  In the end, I connected the input pins to ground across 10K Ω resistors.  This was the winning circuit for the wand and input wires wires:

Circuit Test #2 - Success!

Circuit Test #2 – Success!

Once that was working, I knew I wanted 3 LEDs and a piezo buzzer to use as indicators of the cachers status and progress, plus a servo motor to open the cache door with.  I have used all of these components before, and was able to hook them into the circuit without any problems, except for how confusing the board looked.  Remember to use resistors with your LEDs – they cannot handle 5V directly.  You can read more about my LED experiments here.

Here is a photo of the inside of the bottom part of the cache, along with a Fritzing diagram, which may be easier to read if you try and duplicate it.  I’ve also drawn a cleaner hypothetical version of the circuit diagram (which I have not actually made), which should be much easier to read and build.  You will need to change two digital pins in the code to make sure the cache will still work.

Here is a parts list for the final version, along with a rough cost in USD.  I have no affiliation with the linked sellers.


Programming the Circuit

I used eight pins for this cache – that might be a new record! I also needed three Boolean (true or false) operators to keep track of where the geocacher was in the process of beating the game. These variables are all commented below. After the variables are all defined, the loop just keeps testing those variables to see if the goat outline wire has been touched, if the game has been restarted, or if it has been won.

This cache was themed for the Berkshire Geobash Mega Event, but you could create any wire pattern or outline to meet your needs. So far, this has been my most adaptable gadget cache. Please feel free to take the circuit diagrams and code and create your own variation!

14 Comments on Creating a Gadget Cache for a Mega Event

  1. This is impressive, and I would love to make a version of it. Any chance of getting a component list. I can pretty much figure out what everything is, but I cannot figure out what the small green board is.

  2. fishercacher // January 7, 2017 at 7:02 pm // Reply

    Hi! We are new to this, but trying to create this circuit. I see a small three pin component that looks to be connected to the capacitor? Any chance you can tell me what that is? Many thanks!

  3. fishercacher // January 7, 2017 at 7:06 pm // Reply

    I should have been clearer in my explanation – it is the device the 3 AA batteries are connected to. thanks!

  4. fishercacher (geocaching handle) // January 8, 2017 at 9:56 pm // Reply

    Thanks so much! We are working on our version of the geocache. Thanks for your help and inspiraton, we’ll let you know how it comes out.

  5. David Wagner // February 7, 2017 at 6:58 pm // Reply

    Thanks for sharing all this great info!

    FWIW, you can avoid a 10k pullup resistor, by changing your input definition line, as an example…

    pinMode(goat, INPUT_PULLUP);

    This puts puts a pullup on the input line, inside of the chip.

    Great work! I am starting a version of my own soon!

    • Thanks! I learned about the INPUT_PULLUP mode after this cache. It is handy, although the HIGH and LOW kinda get switched around representing “on” and “off”. I’m still new to the whole electronics thing, and often stop researching once I get something working. But, now I know!

  6. Why the 470uf capacitor? I have built this in my own version, a dragon breathing fire, and it has turned out great… Just need a place to put it where the muggle damage possibilities are minimal.
    Anyway, I am using this same circuit to build an etch a sketch cache which will work on the same principal. Knowing very little about capacitors, I was wondering why this one, and if the value could be different. I don’t have one of these handy and have about 30 others of various values.

    • The servo motor pulls more amps for a fraction of a second than the power booster I’m using can supply from the 3 AA batteries. The capacitor provides the extra power when the servo starts up. No particular reason for 470μF, other than it was the biggest one I had that worked. If you had a capacitor greater than 470μF, it would likely be fine as well. Generally, you can figure out your capacitor sizing using Farad = amps x seconds / volts. Of course, the battery is still proving some power as well, so the calculation is a bit rough. If you’re new to electronics, be careful with capacitors – the bigger they get, the more dangerous they are.

  7. Thank you…

  8. Kent Uhrich // August 10, 2017 at 5:19 pm // Reply

    Hey Eric! On the telephone cord, did you solder it to the eye bolt? I am guessing you twisted the ends together to make one wire out of the phone cable and then solder the to the eye bolt?


    • I did twist all 4 lines together into one, but I just tightened it between two nuts on the eye bolt, and then used a copious amount of electric tape over the whole thing. No solder – I’m not sure a soldering gun could get the eye bolt hot enough, anyway. It’s held together for over a year, now.

  9. Thank you for the speedy response. I am REALLY going to tackle this project. 🙂


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