In part one we prepared all LEDs for the assembly of the cube. Now, we start in earnest...
Step2: Build the groups
Each group consists of eight LEDs. Here they are:
You need a template to assemble the LED groups. My LEDs are 5mm, so I drilled a set of 8 5mm-holes in two rows with 4 holes each into a piece of wood.
Insert 4 LEDs in the upper row of the template. Make sure all anodes point towards North-West.
Bend the cathode leads as shown. To give you a better understanding, the LEDs are slightly rotated in this photo:
Solder the LEDs to their neighbours.Insert the remaining 4 LEDs, again with anodes oriented towards North-West.
Again, bend the cathodes so you can use them to connect the LED. This is now the opposite way (basically all wires are bent clockwise).
Solder them to their neighbours so that the cathodes form a ring-like structure. Align anodes and make sure they are vertical. And then test!
Yes, it works...
Repeat this process another 7 times. You will now have set of eight groups of LEDs. Here they are, hinting at their later organisation.
Step3: Assemble the cube
Finally, all groups are connected. This step needs to be executed carefully. Make sure everything is level and aligned.
Insert the first group into the perfboard.
Then, add a second group. Put it on the perfboard in exactly the same orientation. Later, the columns of these two LED groups will be connected in parallel.
Now, you should do something that I only did after I had the cube finished: Connect the common cathodes to the perfboard. I wanted that connection to be invisible, so I put each vertical wire in the middle of its group. Better add them while adding LED groups, because access is easy now.
Here is a top view of the finished cube, with those vertical wires marked.
Now test those first two groups!
If everything works, start with the second level. Connect the two groups of the second level through their anodes to the corresponding anodes of the first level. Take your time! To make sure everything looks even, just start with two connections on opposite corners. If everything looks good, connect the rest.
This should be the moment for you to understand why half-cubes (i.e. groups of 8 LEDs) are easier to assemble. All solder locations are accessible from the outside. Of course it is a bit more difficult when you connect the second group of a level, because the first group gets in the way. But it is still easier that connecting a whole level at once.
Here is a side view of the next two groups.
Again, add the cathode wires and test. Add Half way there!
Keep going with the next level.
Finally, add the top level.
As mentioned before, the corresponding columns of the two half cubes have to be connected. Like so:
And this is the end result. The perfboard is cut so that the cube just fits on it. The rest of the board is used for the electronics.
Make sure everything works. Try all combinations of columns and levels. If you didn't know what multiplexing means: You are doing just that. Manually, of course. But that is what we have a controller for. And of course we can make the 8 LEDs of each group light up at the same time.
Congratulations! This is the hardest part done. What remains to be build is the electronics to control the cube. It is very simple. See part 3 .