Remember LED cubes? We sure do — they were all the rage for a while, and then it seemed like everyone just sort of lost interest in them. There are probably a lot of reasons for that, not least of which is likely the amount of work it takes to put one together from discrete LEDs and separate pieces of wire. Could there be a better way?
Of course there could, and [Sasa Karanovic] thought he had it all figured out with this PCB-based LED cube. At first glance, it seems to make perfect sense; after all, weren’t PCBs invented to take the place of all that pesky point-to-point wiring in the early days of electronics? The boards [Sasa] designed are pretty cool, actually. They’ve each got room for 16 addressable WS2812 LEDs in 5 mm packages, with every possible bit of substrate removed to block the minimum amount of light. That left very little room for traces on the 2-mm-wide arms, so the PCBs had to have four layers, which raised eyebrows at the PCB house when [Sasa] submitted the design.
Such an airy and open design obviously has the potential for mechanical issues, which [Sasa] addressed by adding pads at three corners of each board; a vertical PCB connects to each LED board to provide mechanical support and distribute signals to the LEDs. The cube seems solid enough as a result, and even when handled the LED boards don’t really flop around too much. See the cube in action in the video below.
What’s nice about this design is the perfect spacing between the LEDs in all three dimensions, and the way everything lines up nice and straight. That would be really hard to do with wire, even for the most practiced of circuit sculptors. [Sasa] seems to agree, but still deems the build a failure because the PCBs block too much of the view. We suppose he’s got a point, and we’re not sure how well this would scale to an 8×8 cube. We’re not sure how we’d feel about paying for PCBs that are mostly air either, but as failures go, this one still manages to be pretty successful.
If this were a kit, I’d buy it.
Me too. And if he’s not putting in in his shop, how about open sourcing the design?
The PCBs don’t obscure the view of the LEDs too much if you’re looking at it from the right angle.
There’s something very similar to this on Tindie https://www.tindie.com/products/feral_makes/5x5x5-rgb-led-cube-with-spectrum-analyser-function/
Might work better if blue or UV SMD LEDs were used on both sides of the PCBs, with a big ball of phosphor goo encapsulating each pair of LEDs.
No idea if that goo is readily available or easy to apply.
It’s easy enough to source of you’re willing to wait for shipping and then mix the phosphor into epoxy yourself. Not even expensive though, I think it’s a good idea.
You would lose RGB unfortunately, but I think it’s a clever idea. Maybe an smd argb, and a glob of diffuser rather than phosphor?
Some FR4 boards fluoresce under UV already, and at least one shop has experimented with producing transparent boards.
Maybe make the PCB layers out of flexible film like an LCD screen connector. Say, two conductors and two sheets per layer with a clear apoxy filling for the sandwich. No doubt there’s probably an smd led equivalent somewhere. It could be possible to make it with a single layer of flexible pcb, maybe double sided and dipped in clear resin, so it just coats the PCBs all the way around for support.
This. And mount the flexible PCB on clear acrylic. You can get WS2812B in very small SMD footprints, 0402 and smaller.
For a nice LED cube you should not use a LED that only shines on one side though.
The whole magic is that the lights are floating in space.
This. And mount the flexible PCBs on clear acrylic sheets. WS2812B can be had in very small footprint, under 0402 IIRC.
It’s a good example of how solving one problem can create another. In this case, making the spacing between LEDs uniform by way of a PCB meant blocking out some of the LEDs in the finished product. Still, I think the idea is genius. Maybe there’s some sort of compromise possible, like with sheets of clear acrylic with channels carved into them for the LED leads. It would still solve the “uniform spacing” problem but allow for the best transparency.
Don’t flood power/ground (actually calculate the amount of copper needed, it’s not hard in this case) and void soldermask wherever there aren’t any traces. If you make the PCB as thin as you can, FR4 would be fairly transparent and really difficult to see in lighting. Can probably reduce the copper even more by using all 4 corners to provide power/ground.
I’d probably use flexible ultra-thin “Ribbon” PCBs.
But rather than use a single large sheet, i would exploit their thinness and have them be ribbons that are to be stacked at the leds themselves to save on empty space and possibly enjoy bulk savings. Would require some extra thinking on vertical supports though.
I think I would start with a string of (commercially made) individually addressable christmas lights, and then make an acrylic holder which keeps the lights in a cube.
Here are my suggestions: In a dark environment plain FR4 PCBs with NO coloured soldermask would do better thn black soldermask, the light would atleast partially shine through the FR4. The FR4 would almost “glow” a little near each LED. The copper traces inside would block light, but they are much thinner than the PCB structure. The effect of the structures blocking light is probably less noticable for bigger matrices, 4*4*4 shows them noticably, 8*8*8 would likely be less so, they only block a small area and there’s be many more LEDs not aligned so as to be blocked from any viewing angle. Also, for a more “point cloud”y effect, perhaps SMD LEDs, with one on each side of the board at each vertex point.
Yeah, I gave trying to build the RadioShack 3x3x3 LED Arduino shield.
It was constantly bending and breaking.
EDIT: ^gave up^
Rather than soldering all those LEDs, he could have used SMD LEDs assembled by the PCB manufacturer, and have 3 holes around each LED to insert a bulb-shape 3D printed housing (clear PETG). The housing would diffuse the light and can just snap into the holes on each PCB. The bulbs can be glued as well… either way his assembly time would be significantly shorter.
Instead of having the pcb go in x- and y-direction: Why not do individual columns in z-direction?
FR4 should be stiff enough to stand upright…
(You’d only need a base to solder them to)
A while back I made a version of a 6x6x6 Neopixel cube, using a base PCB and columns of LEDs on single strips each. For the strips I used thin PCBs (I think 0.6mm?), made them as narrow as I could, no ground planes so they could look as transparent as possible. Here is a demo:
https://youtu.be/A8KgOq3c2zw
I swear it looks better in person than on camera :) The main challenge is that as the PCB strips are so thin, they are wobbly and shake quite a bit. An acrylic enclosure will probably help. Each strip has a 2×4 right-angle pin header at the bottom which plugs into matching headers on the base board. The base board has a ESP8266 to control the display patterns. I was going to make it a kit but then the pandemic happened, so that was the end of it.
I also made a version using SMD LEDS (single colors though). But the SMD LEDs have even smaller angle of view so if you stand from the back it’s hard to see anything at all:
https://photos.app.goo.gl/YdZZBN3uVRn2KCJq9
Looks pretty cool, clever idea to use columns!
I created a cube and tower using 0.8mm PCB. The leds are common anode, and there are led drivers and an ESP32 on the bottom layer.
https://www.2dkits.com/zencart/index.php?main_page=product_info&cPath=5_8&products_id=87
https://www.2dkits.com/zencart/index.php?main_page=product_info&cPath=5_8&products_id=102