On the one hand, the cube works brilliantly (pun intended) and looks cool. On the two hand it is a royal pain to put together. What if...
I had been clinging to the idea of having individual LED boards, but for no good reason. This was an outgrowth of my original, fully connectorized cube and perhaps some subconscious influence from seeing other cube designs. There was no compelling reason that I couldn't rethink this, so...I did.
I sketched out some ideas for combining all of the LED boards for one level of the cube onto a single PCB. I would still use 2mm headers as before, but here's the rub -- I only needed two of the 2x2 headers instead of 8. For a full cube, I now needed 16 of them for a cost of....wait for it...$2.32!
Well, not so fast...
I thought about it some more and figured that another way to reduce construction complexity would be to use press-fit connectors instead of soldered thru hole headers. Press-fits allow the builder to simply press the LED board assembly into the holes on the base board. No soldering required (but you can solder them as well if desired). The connector pins fit snuggly into the corresponding base board holes and would allow for very rapid assembly. An added benefit is that the boards would self-align due to the snug fit of the connector. They have the added benefit of making disassembly possible too.
Based on the first prototype build and the concern that two of the pin headers might not easily hold the weight of an LED board without sagging, I decided to add holes for 2 extra headers to the base board just in case they are needed for stiffening.
The press fit headers are more expensive and I have to look into second sourcing. If two of these are used per LED board, the total cube cost is: $7.52. I can reduce this a bit by replacing two of the 2x2 with a single 4x2 on each board for a cost of: $6.25. This represents an over 80% reduction in connector costs from the original design idea.
After lots of crumpled up pieces of paper I think I’ve found a winning combination of price and ease of construction by using press-fit headers. The builder is now faced with eight super simple solder connections per LED board. Beginners at soldering should have no problem with this.
A final benefit is that switching to a single 4x2 header meant that all the little fingers coming out of the sides of the base board would go away, leaving a more streamlined, elegant appearance.