8x8x8 LED Cube



Summary

I'm not sure when I first saw a video of an 3-D LED cube. However, it was around December of 2011 when I started to design my very own. There are lots of videos out there on Youtube displaying single color cubes. While these are cool, in my opinion the cubes built from red/green/blue (RGB) LEDs are much more awesome. While they are more awesome, they are also much more complicated to build. Somehow, instead of getting a single signal to each LED (to turn it on), you need to get THREE (one for each color)! If these things fascinate you as much as they me, and you want to build your own, be prepared to spend around 40 hours constructing one (for an RGB).

See the best game I've written for it so far on Youtube here.

Learn From My Mistakes

Unfortunately, I had to construct two of them! There were two reasons for this. The first: cosmetic. I bought the wrong kind of LEDs the first time around - I didn't realize they weren't "diffused". Having diffused LEDs makes the display significantly better. The second: My initial design and assumptions were flawed, in that I didn't fully understand the voltage requirements for the LED driver chips I chose. Subsequently, I applied too much voltage to the high side of the LEDs, and it ended up frying the chips that drove the LEDs, which led to several rows of LEDs being fried. I don't know how many hours I spent troubleshooting and replacing LEDs, only to have anomolous strings of LEDs faintly lit, etc. The cube was broken beyond repair. So I decided to start over fresh, buy the right LEDs, and rebuild the controller circuit. Success!

Step 1. Preparation

First things first, you need LEDs (Diffused ones, as I mentioned above). If you're patient enough, I recommend getting them on ebay from some source in Hong Kong. You can get packs of 100 or 500 for a LOT cheaper than buying them bulk on Digikey or another site like that. I'm talking saving hundreds of dollars here.


Next, you'll have to straighten out a bunch of galvanized steel wire. I chose 22 gauge wire. It's thin enough that you can straighten it easily, and it takes solder well. It's also strong enough to act as good frame support for the cube.


So how do you straighten of bunch of wire that came from a spool? I had to look this one up. One of the more popular techniques is to stretch each piece of wire until *just* before it breaks. To do this, use a "C" clamp, or whatever clamp you can find, to hold on to one end of the wire. If your clamp is mounted to your workstation, that's good. I just chose to slide the clamp onto my door handle. Now, grab the other end of the wire with a pair of needle nose (or similar) pliers. Slowly pull/stretch the wire toward you, and you'll start to feel the wire stretch itself out. You'll probably break the wire your first few tries, so be sure to have extra! Each time you do it, you'll get better at knowing how far you can stretch it without breaking it. Once it's straight, carefully unscrew the clamp off of the other end, and place it aside. For an 8x8x8 RGB cube, you need to do this over 250 times (4*64 plus a few extras for cross beams). I quickly caught on that I could cut the wire to twice the length a side of the cube, and only need to straighten half that. Trying to straighten wire much longer than that gets very hard.


Step 2. Build a Frame/Jig

So how do you get nice and consistent rows/columns of LEDs? You'll need to build a jig. I still have a bunch of Legos from my childhood, so I decided to try to use them. Luckily, the Technic bars' holes are just big enough that you can insert an LED into them, and it fits snugly enough to stay.


Before you start populating the jig with LEDs, you'll need to bend the leads appropriately. This is a very boring and tedious process. Which leads you bend in which directions will change based on your design. Ultimately, you need to bend two of the signal leads in one direction (90 degrees) and one signal lead in the opposite direction (90 degrees) of those two. The fourth lead (the common anode/cathode, depending on your design) can remain straight.

Step 3. Build Your LED Planes

Now you can begin the long and laborious process of building 8 planes of LEDs. Each plane consists of an 8x8 grid of LEDs. Take your straightened wire from before, and begin laying them down, using the Lego pips/dots as guides.




Careful when you're clipping the excess wire, these things can move, baby!


Step 4. Align the Planes

For my first version, I bought some clear plexiglass at a local hardware store. I recommend using black ABS plastic, which I used in my second version (and seen in most of my Youtube Videos like my Asteroids one). Carefully measure the distances between all of the wires on any of the LEDs. It's easiest to measure using a bottom LED. Also measure the distance between LEDs when they're still in the jig. You're now ready to mark on the base plastic where you need to drill holes for the wires to go through. The more precise you are in this step (all of the steps require precision...), the better it will look in the end. Drill your holes and begin the tedious process of aligning the wires in a single plane into the holes in the base. It'll help to tilt the plane to one side and work your way down from one end to another.


Now you'll need to connect all the planes together. I borrowed a long Technic piece from my jig so that the planes were equally spaced apart. Starting at the top, solder a wire perpendicular to each of the planes, the full length of the side of a cube. This wire connects each of the planes' row to the corresponding row of the other 7 planes.


Step 5. Getting Signals to the LEDs

I figured I'd want the capability to easily remove the controller circuit from the cube, and so I didn't want to hard-wire the signal cables directly to the controller. Instead, I chose to put headers on the controller board, and make custom connectors that plug into those.



The Finished Product


Schematic and PCB