- The PCB has to be an approximation of ball with as many faces as possible
- The final outer diameter of the ball has to be at most 20 mm
- The ball has to run from Li-ion battery voltage 4,2 .. 3,0 V
- The unfolded PCB dimensions should fit within 50 mm x 50 mm square space for less expensive manufacturing
- The portal fluid ball consist of flex PCB folded into truncated icosahedron. The same structure which has the soccer ball. There is one RGB LED on every face of the polyhedron. The polyhedron has 32 faces which is enough to create illusion of moving light around the ball of portal fluid.
I have found the smallest RGB LED - APA102 in 2020 package. In comparison the SK6812 LED has simpler wiring, but it has too large package for my project.
PCB is intended to be fully flexible dual layer. The PCB will be mounted on 3D printed support structure. Vias are located in non flexing area. On each of five arms there is non covered flap, which mates with other arm. These flaps are intended to be connected by solder and mechanically fasten the polyhedron. On two dead ends of each arm there are flaps without uncovered wire. These flaps should be held down by neighbour arm. It is kind of interlocking structure. These interlocking flaps were missing on my first paper model.
Connection of the whole polyhedron to external circuits is made by soldering pads on the root pentagon. Vcc and GND are located on different sides of the PCB, thus the Vcc cable has to pass through the hole in root pentagon. Data line pads are located on outside of the polyhedron.