We're going for it now, 612 LEDs, 51 of them controlled by a single IS31FL3733 chip

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Bunch of IS31FL3733 on a pentagon PCB controlling a bunch (76? - 106? - 128? - 181?) of RGB LEDs. It's 51. Was hard enough to route anyways!

Everybody's doing it, my hackerspace has this thing for dodecahedrons and I thought that would give an interesting challenge.

Trying to find a sweet spot of LEDs and controller.

  • mistakes been made

    davedarko12/30/2021 at 11:38 0 comments

    I missed that one LED wasn't correctly placed in the schematics and one connection is missing. Have to go in with magnet wire and fix that on all 15 boards :)

  • shapes

    davedarko12/17/2021 at 19:33 0 comments

    Always tough googling something when you're looking for the name to google in the first place. I needed the "dihedral angle" of a dodecahedron, meaning the angle between the sides / faces of the body. It's 116.56505°. The cool thing is, with that Angle I can basically nibble away all sides and have the perfect folding angle for this! But for now I just eye-balled it.

        cylinder(3, 35, 33.15, $fn=5);
        union() {
            color("red") cylinder(1, 30 , 30, $fn=5);
            color("red")translate([0,0,1]) cylinder(2, 32 , 31, $fn=5);
    translate([-31, -25, 6]) rotate([ 0, 116.56505, 0]) cube([5,50,5]);
    screenshot of openscad, a small frame for a pentagon shaped object is shown. A little bar in an angle is close to it.
    Screenshot that compares the angle of the block to the manually set angle of the frame, so it can fold up to a dodecahedron. Angle is basically indistinguishable.

  • First boards are ordered after 2 years

    davedarko12/15/2021 at 17:02 0 comments

    Since I'm visiting family in America, I found some time to tackle those weird PCB designs that I always talk about, but never do. Two years ago I made the #Do or Donut SAO  , which rhymes with this project as in me using the same(?) chip to control a bunch of LEDs. When I started this, two things came clear: I did not want to use more than one chip on a board and that basically meant going for 51 LEDs. You can read up on all my minor design choices and routing issues on twitter:

    The distance between the LEDs in not the same at all, as the five triangles that make up the pentagon have angles of 72-54-54 degrees and are there for not symmetrical in all the directions. But I'm happy with the spacing, so I proceeded.

    I should be able to power everything with a considerate brightness from a smaller battery, as was the LED cubes I took inspiration from. Heat should not be a problem either, but we'll see about that. The dodecahedron will have a height about 5cm.

    The chip can have up to 16 addresses, so that's perfect for controlling the 12 boards with one IC. I have not calculated the frame rates of anything, the chips talk I2C with up to 1MHz, to up to 12x16 LEDs. 

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Xasin wrote 12/30/2021 at 13:56 point

I'm wondering how well this would have worked using WS2812-Mini LEDs.
If you look at someone like CoeleCan't on Twitter, they are driving giant RGB Matrices made of NeoPixel-Style LEDs using a Teensy, and the results are quite impressive. That would also reduce the routing complexity of these PCBs.

Apart from that this is already looking really cool, I'm quite excited to see how well it'll work!

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davedarko wrote 12/30/2021 at 21:06 point

in short: 612mA for all neopixels at (0,0,0) was a no-no for me, but that giant project sounds nice. At that size routing would probably a bit tricky, but I can see why one would think about going that route. Also the board is routed, so that's nothing to worry about anymore :) 

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Xasin wrote 01/02/2022 at 12:44 point

Ohhh right, I almost forgot about the notoriously bad standby power use of NeoPixels... Ehh.
To be fair, it's also more fun to do something a bit more efficient and challenging like routing a matrix.

Can't wait to see the finished dodecahedron <3
Will it actually do something proper, or just look really, really cool?

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davedarko wrote 01/03/2022 at 00:25 point

I got half of it "done" now and there's still some more to do to make it portable :) I'm thinking about adding a gyroscope so I can work with gradients and fake shadows. Preferably write a selfhosted ESP32 web page where the JS can map images to the cube.

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Xasin wrote 01/03/2022 at 09:33 point

Ohh whew, good luck getting gyros, those things are hard to find!
I just dislike how everything is kinda out of stock, so designing projects is a challenge just because you don't know what's around.

An ESP32-C3 could fit into the dodecahedron nicely, and using a self-hosted static website is a smart move!
Always wanted to do something like it and even got the basic API structure and libs done.

Keep me posted, that sounds very fun :)

  Are you sure? yes | no

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