It’s been very long since my last update, and a fair bit has happened.

Hardware:

I did a rev 1.2 of the board and sent them off to allpcb for a small run (10 IIRC, so 120 of the LED boards and 15 of the end boards).

The boards showed up quickly, and didn’t work. Well, two of the LEDs worked sometimes, but the third would not.

Clever me, I did some led moving and I managed to route the VCC line for LED #2 right across the data out pad when I did some moving. I could break the pad by hand and get them to work, which through trying to be quick led me creating a circuit that would work for all the colors except white because I didn’t break the trace completely. Which led me to think a new real of LEDs was bad and waste a couple of days trying to track down what was going on.

I took the opportunity to do rev 1.3:

I bumped the VCC and ground tracks up in size, redid the VCC routing, and just generally cleaned things up to be nicer. I also added (finally) a 100 nF decoupling capacitor to the right of the #1 LED, which should help eliminate glitches in the future.

I spun a small verification order (3) through OSHPark because it was only $5, and those worked great. After that, I pulled out my little list of material costs, went back to reprice the PCBs, and found that JLCPCB would do my full first order for $83 delivered, which was about 30% less than the $120 I had written down. Given the temporary nature of PCB special deals, I put that order in, and today found this on my doorstep:

 The new boards arrived from allpcb.com. To recap, this, time I went with standard 0.1” (2.54mm”) header pins between the boards. I ordered some angled headers from the Amazon to use for the connections.

After I populated 11 faces with LEDs, it was time for assembly. Here’s the first approach:

The first concept was to wire the faces together with short pieces of header on the back. This worked poorly; it took a long time to hook them up and the angles were rarely right. The first half was technically done, but I was unhappy.

For the second half – and keeping in mind that prettiness was not a requirement – I decided to go with another approach. I would use angled headers on the outside, and just solder the pins together where they overlapped.

But first, I needed a better way to set the angle. The led to the following design in TinkerCAD:

And then a long session of setup to migrate my 3D printer from an absolutely ancient laptop to one that was merely old. I printed up a whole set of these, and then used them to hold the faces at the right angle for soldering. That resulted in this upper ring:

The alignment clips on the right worked very well; it only took about 30 minutes to do this whole ring. And yes, it’s very ugly.

Time to hook them together, and then attach on the end face. These are attached with small pieces of header pin on the outside.

Then it’s time to wire up the 5 volts, ground, and data, and take it out for a spin.

The first attempt was not successful; one ring lit and the other didn’t. A quick check discovered that the ground connection between the two rings was not functioning, so I added an additional connection. Which led to this:

The driver is running some simple rainbow code, so each LED is a slightly different color.

Finally, adding on the requisite acrylic globe gives us the following:

Globe of fire from Eric Gunnerson on Vimeo.

Overall, I’m mostly happy. It would be nice if the header holes were a bit tighter on the pins, and I could clearly get by with 2mm or even 1.27mm pins. The 3d-printed alignment clips could use another iteration to make them easier to use.

A week or so goes by, and I get a package back from allpcb, so I started building one.

Each half has a ring of 5 pentagons plus one the end, so I started hooking 5 boards together:

The WS2812 LEDs are only 5mm on a side, so the whole board is roughly 15mm x 17mm. That’s tiny, and frankly working on it was a huge pain. I did this, put the boards into a box, and closed it.

Then I came back the next day and decided to have another try. Rather than connect on the outside, I decided to use a much lighter wire and connect on the inside (back) of the boards. Here’s a set of 5 with VCC and GND hooked up:

Yes, that’s some *ugly* soldering, but in my defense I’d like to note that the spacing on the holes is about 0.05”/1.3mm. This then gets folded into a ring. Eventually, we end up with the top and bottom:

Next, those two are soldered together with wires to carry VCC and GND between halves, and you end up with this:

Next was to wire through the data ports. Basically, it starts at one face at the open end, goes around that ring, goes around the lower ring, and finally travels to the bottom. Add in some hot glue to help hold things together, and put the LEDs on, and here’s the result:

That is one ugly bit of construction, and it took a lot longer than I had hoped.

After soldering a few hundred WS2812s, you learn how to do it without burning them up. On the left is one face from the 3-LED version that I tested to verify the layout.

V1.1

The first version was technically a success, but only because I so cussedly kept on. I was wondering if I could make something small enough to fit in an ornament ball, and the answer is “yes”, but you really don’t want to do it.

So, it’s practically a failure.

The biggest problem is the connection between the faces; the holes are too hard to solder, and using individually-cut wires is a pain…

So, I’m going to abandon the single-LED version (kindof – more on that later) and work on the 3-LED version. I started by going with standard 0.1” (2.54mm) header spacing, and the plan is to use angled headers. The angled headers will stick out to the side, and two faces are connected by soldering the ends of the header pins together. It’s going to look a big weird, but should be a lot easier to construct.

Here’s the old design and the new one:

Obviously, the big different is the connectors; they are much larger, though the overall design is only a big bigger. I’ve used the extra space to pull the LEDs a bit farther apart because trying to hand-solder the LEDs in the first version was a difficult. And I added a little bypass jumper; if you solder a wire (or better, a 0805 zero-ohm resistor) across those pads, you can omit the bottom two LEDs and things will work fine.

If you read backwards, you might see that it says “Dodecahedral Light Engine” on the back, which is the new name for the boards.

A fully-populated DLE will features 33 LEDs, pull 2 amps @ 5V with everything on white, and put out quite a bit of light.

I need one more design review pass before I send this one out to have boards made.

The parts for the new controller have started trickling in, but until they all show up I’m a stuck there, so I’ve been thinking in other areas.

In the olden days – pre LED – I had a number of the 50 or 100 light globes in my display:

I liked them for their intense burst of light, but the ones I had gradually died, and I haven’t found a replacement.

So… I got thinking again about options. When I built my Animated Snowman, I used WS2182 leds on the faces of 3d-printed dodecahedra. It worked fine, but the hand-cabling was a pain:

Using the acrylic lamp globes worked great, however. They are cheap, easy to get, and fully waterproof. I just needed a better way to get the LEDs in place.

One of the nice things about dodecahedra is that the faces are all pentagons. I remember a hack-a-day article a couple of years ago when somebody built one by soldering pc boards together, so I decided to do a design of that what that might look like:

The concept is that any face can hook to any face. You wire up the ground and VCC connections on all faces to give rigidity to the dodecahedron, and then wire up the DIN and DOUT connections from face to face in whatever pattern makes sense.

This design gives me 12 LEDs (well probably 11, since the top or bottom one will be used for support) in the space of about an inch, so that would easily work in the small acrylic balls (6”, or 4” if I can get them).

Of course, why do one LED per face when you can do 3:

Same concept as before; hook up DIN from another face, it will chain through all three LEDs and then head out through DOUT.

This board is roughly an inch in size, so the resulting dodecahedron will be around 2” in size. That will give us 33 LEDs and live up to the title of the post, but it may be overkill, which is why I’m going two versions. I’ll drill a hole through the 12th face and use a threaded rod and nuts to mount the DLE (Dodecahedral Light Engine).

I need to do some design cleanup and then send off for a run of these to see how they work.