So I’ve started on the LED matrix.
I have finally decided on how I am going to structure the matrix, but after creating 2 planes, I already regret one of my decisions 
Although it’s probably a minor thing.
I thought about how each LED in the matrix should be mounted, and came up with three points:
- Too many brass rods will block the light.
- If you place the support rods close to the LEDs, they will cast a fairly large shadow.
- Too little brass rods will cause the cube to become unstable and wobble when moved.
With this in mind, I came up with this design:
RGB LED close up.
I decided to use 1 brass rod for every row and column in a vertical plane. It might be a bit overkill. I believe eightcubed only uses 3 vertical rods per plane, but you can’t really make a uniform distribution of rods if you go higher than 2, which is too weak. I decided to go for a uniform look, and think the extra rods will provide a bit more stability, hoping they won’t block too much light 
I could have used a different orientation on the LED to have the leads all point in the same direction. However, since these are 5mm RGB Leds, the 4 leads are really close together. Bending them like this makes for a better “distribution” of the space between the leads, and puts them a bit further apart which leaves me a bit more room for error
As you can see, there is quite some space between the vertical support rods and copper wire, and the LEDs. As noted above, I did this to reduce the shadows cast by the rods. The result is actually quite nice. After finishing 2 planes and putting them together however, I noticed that the 3 horizontal leads block quite a bit of light if you view the cube from the top. I’m not starting over But were I ever to make a second cube, I would place the copper wires closer to the LED. The copper is 0.2mm and doesn’t cast a big shadow, and this way the length of 2 of the 3 leads could be reduces, which makes the cube slightly more transparent
With 2 planes finished I’m rather happy with the result so far. I will finish 8 planes first before I go and try to build the cube. I’m building vertical planes. I guess this way it will be easiest to de-solder an entire plane, and take it out if any repairs need to be done to a single LED. Making vertical planes means de-soldering the brass connections on the outside and bottom and lifting plane out. Making horizontal planes would mean de-soldering all the LED cathodes, which is 3 per led I test every LED, row and plane before putting it in, so I don’t expect any problems, but hey, better be safe then sorry right? 
Well, that’s it for now! Don’t know when I’ll be making my next blog post, since the next part is just a WHOLE LOT of soldering work to do. After that I’ll start on programming a single led driver, to decide on my circuitry based on what I’ve learned from that
Talk to you later!
Wracky.
hi, how do you controll these? doyou have a sketch?
Hi iduktech, and thanks for commenting!
I don’t have a final design yet, but I’ve learned a lot from vespine.
I’m planning on using 12 TLC5940 LED drivers which should give me enough channels for 192 leds (64 dots per layer, RGB per dot) and 8 mosfets to multiplex the layers. I’m going to try a 100Hz refresh rate on the cube, like vespine did. The TLCs will be daisy-chained. I’m not sure if I can pull off a chain of 12, but I could also split them into smaller chains. The MOSFETs and TLCs will be driven by a microcontroller. (I use the Pic32 starter kit).
The TLCs control the current per LED. The MOSFETs switch the horizontal layers. Since the TLC drivers supply a constant current sink, these have to be common ANODE leds. All the anodes will be connected per layer, and the TLCs give you column adressing. FUN!
I will do a full article on my design once I’ve figured out how I want it exactly.
Hope this helps!
Wracky.