Roled Cube is made of 1,728 RGB LED. With a spacing of 4cm we have a cube of 49cm-large. With this size it has to be solid and resist to the weight of the LED and the wires.
The constraints are to direct the LED to the upwards, to minimize the number of wires on each side, to minimize the number of wires to descend through floors.
First of all not to have 1728×4 (3 anodes and one cathode) wires, we decided to use multiplexing, so all anodes of a same floor are connecting together and on each column all cathodes are connecting together. So we have 144×3 = 432 wires at the bottom of the cube and twelve (the twelve anodes) to descend in the cube.
To minimize the number of wires on each side, for each LED the three cathodes are soldered on a different side of the cube.
In order to make a straight and uniform cube we made like a comb in wood to create each column and solder 12 LED with straight wires. Once we have our 144 columns, we solder them 12 by 12 to make a plate, which will be vertical. With our 12 plates we make a cube.
Finally, we didn’t want 444 wires connected from our cube to our mainboard, so we decided to make a giant PCB under our cube with our drivers of LED, and our cube is directly soldered on the PCB. We only have the wires for the bus connection between the drivers and the mainboard, and for the anodes.