Roman Dodecahedrons: A Mystifying Archaeological Find

Much about archaeology can be described as trying to figure out the context in which objects and constructions should be interpreted. A good example of this are the metal dodecahedrons (twelve-sided shape) which have been found during archaeological excavations at former Roman sites. Since 1739 over 115 of them have been recorded, most recently a fully intact copper specimen found near the Lincolnshire village of Norton Disney during the Summer of 2023 by a local group of archaeologists.

Two ancient Roman bronze dodecahedrons and an icosahedron (3rd c. AD) in the Rheinisches Landesmuseum in Bonn, Germany. (Credit: Kleon3, Wikimedia)
Two ancient Roman bronze dodecahedrons and an icosahedron (3rd c. AD) in the Rheinisches Landesmuseum in Bonn, Germany. (Credit: Kleon3, Wikimedia)

As the Norton Disney History and Archaeology Group notes on their page, this is the 33rd example of one of these items found in what was once Roman Britain, lending credence to the idea that such dodecahedrons originated within the Gallo-Roman culture.

As for the objects themselves, the ones so far found were dated to between the 2nd and 4th century CE, are all made out of some kind of metal alloy (e.g. bronze), are usually a dodecahedron but sometimes different (e.g. an icosahedron with 20 faces), yet all are hollow and usually with a single large hole in each face. The dodecahedron found at Norton Disney was analyzed to consist out of 75% copper, 7% tin and 18% lead, with a width of 8.6 cm and weighing in at 254 grams.

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This Infinity Dodecahedron Build Shows All The Tricks

The infinity dodecahedron is one of those super eye-catching builds that many of us hardware hackers have on our ‘build one day’ project list. The very thought of actually doing it strikes a little fear into the heart of even the most intrepid maker, once you start to think about all the intricate little details and associated ways it could all go horribly wrong. Luckily for us, [Hari Wiguna] has documented his latest build as a long video build log, showing lots of neat tricks and highlighting many problems along the way. With the eventual goal of removing many of the issues that make such a build tricky, [Hari] hopes to make it practically easy. Let’s see how that turns out!

HASL-finished castellated (half hole) edge contacts make butt-jointing a breeze

A common route for such a build relies on appropriately shaped 3D printed frame parts, with some kind of clear plastic for the 12 faces, and LED strips stuck to the inside of each of the 30 edges. Whilst this works, [Hari] thought he could do a bit better, using butt-jointed PCBs as the frame material.

The PCBs handily double up as something to solder LEDs onto (because that’s what PCBs are mostly intended for!) as well as a way to pass power and data signals around the frame in a minimally visible way. As will become obvious from the lengthy discussion in the video, a few simple tricks here and there are needed to make this strategy work. With the recent proliferation of PCB modules using castellated edges for termination, the usual Chinese PCB fab services have all started offering very good value services for this feature. Once a PCB feature that was a specialized (read that as ‘expensive’) offering, it is now quite affordable on your average maker’s budget.

Data path planning? Just use paper and tape!

One immediate practical issue was how to pass the data connection around from edge to edge, given that there are three edges per vertex. The solution [Hari] came up with was simple, just duplicate the signals on each end of the PCB, so the data out signal can be tapped from either end, as required.

Even with 3D printed jigs to hold the PCBs at just the right angles, there’s still some wiggle and a little risk of edges not quite aligning, due to accumulated errors around the frame. It did come together in the end, with the expected spectacular visuals. We’re sure many of you will be waiting for [Hari] to release the next version of the design to the community, hopefully with even more of the ease-of-build issues resolved, because we want one even more now.

Naturally, this is by no means the first infinity platonic solid we’ve seen, here’s a smaller one for starters. If you remove the mirrors and LEDs, then you’re just left with a plain old dodecahedron, like this cool folding project.

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Wonderful Foldable Printable Dodecahedron

Debra Ansell of [GeekMomProjects] fame came up with a neat, 3D design that prints flat and then folds up into everyone’s favorite Platonic solid: a D12.

Why would you want to do this? Well, folding up your 3D prints gives you a third dimension “for free” without using all that support material. Here, all of the outside faces of the dodecahedron are printed flat against the build plate, which is probably the nicest side of your prints. And embedding LEDs in the resulting shape would probably be easy because they’re all in plane. And speaking of LEDs, we kinda expected to see them here, given Debra’s motto: “LEDs improve everything” — that part is up to you.

Debra notes that she likes PETG instead of PLA for the extra strength in the thin-printed hinges, and we’d bet that your printer’s tolerances will need to be spot on for the clips that hold the whole thing together. (We’d be tempted to apply a little super-duper glue.)

As always with Debra’s projects, there’s some creative solutions on display here that’ll help you out whether you need a D12 or a D20, so give it a look!

Thanks [Peter] for the tip.

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Dazzling Desktop Dodecahedron

Much like us, [AGBarber] digs all the infinity polyhedra already out there, but laments the fact that almost all of them are too large to be used as desktop distractions conversation pieces. That’s probably because it’s a lot easier to build ’em big, but that didn’t stop [AGBarber] from trying, succeeding spectacularly, and paving the way for anyone who wants to take on the challenge of building a dazzling desk toy of their own.

We all know that all those little strips of LEDs have to be chained together somehow. Wires would work fine in a larger version, but at roughly softball size, they become a tedious and fiddly nightmare. So what did [AGBarber] do instead? That’s right, they designed two different types of custom corner PCBs. The 3D printed brackets that hold the LEDs and the panels together are no cakewalk, either — [AGBarber] recommends using a resin printer if you have access to one, though it isn’t strictly required.

Everything about this project is open source, including a bonus printable jig for gluing the brackets together at just the right angles. All the steps are well-documented, from applying the mirror film to programming the Wemos D1 mini that controls the lights [AGBarber] programmed in a ton of animations, too, which you can watch after the break.

Want to build a small infinity thingy that isn’t quite so difficult? Crack open a cold one and check out these cool coasters.

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Bucky Glow: Have A Ball While You Practice Coding

About a year ago, [Jonathan Bumstead] built a giant, touch-sensitive, interactive RGB LED geodesic dome that somehow escaped our attention entirely. For this year’s Hackaday Prize, he’s designed a smaller version that’s just as awesome, but a lot faster and easier to build.

The Bucky Glow is great way for hackers of all ages to expand their coding and problem solving skills. This interactive dodecahedron consists of 11 RGB LEDs and a Nano inside 12-sided laser-cut MDF sculpture. The breakout header means you’re free to add interactive bits like a DIY capacitive touch keyboard, IR sensor/emitter pairs, motors, or whatever you want.

When it’s time to relax, Bucky Glow puts on a light show. It comes ready to party without any programming necessary, but if you wanna put on some Pink Floyd and get your hands dirty, [Jonathan]’s custom Processing app makes it easy to program complex light shows.

[Jonathan] is currently working on some different Bucky Glow dissemination methods, such as a kit version. For now, you can buy a fully assembled Bucky Glow through the One Bit Kit store. Interact with the break to try it before you buy it.

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Homemade Omnidirectional Speakers In A Unique Enclosure

While studying acoustics in college (university for non-Americans), [Nick] had a great idea for an omnidirectional speaker. Some models available for purchase have a single speaker with a channel to route the sound in all directions, but [Nick] decided that a dodecahedron enclosure with 12 speakers would be a much more impressive route.

To accommodate the array of speakers, the enclosure needs twelve pentagons with a 58.3 degree bevel so that they fit together in a ball shape. After thinking about all of the complicated ways he could get this angle cut into the wood pentagons, he ended up using a simple circular saw!

Once the enclosure was painted [Nick] started wiring up the speakers. The equivalent impedance of the array of 8-ohm speakers works out to just around 10 ohms, which is easily driven by most amplifiers. The whole thing was hung from a custom-made galvanized pipe (all the weight adds up to about 15 kilograms, or 33 pounds for Americans, so the rig needed to be sturdy). We’ve featured other unique speaker builds, but this is the first 12-speaker omnidirectional speaker we’ve seen. [Nick] is happy to report that the speakers sound great, too!