I wanted something fairly easy to assemble so that the focus would be on generating cool blinky content. The goal of any blinky lights project is to, well, blink lights.
This got me onto another tangent -- how to control all the LEDs? Some kits require that you provide a controller yourself, others have controllers built into the kit somehow. I really didn't like the idea of being stuck with somebody else's idea of a controller. I have my own ideas, thankyouverymuch, and I'm sure everyone building a cube has ideas of what they like too.
I now added a new goal to the cube design: allow the purchaser to control the cube using a controller board of their choosing.
An immediate advantage to this is that I no longer had to pick a method to control the LEDs. Let's face it. Regardless of the controller architecture I picked, some would like it and some would hate it. Why not pick your own? Similarly, my product would not have the added costs associated with controller circuitry. This would reduce the kit cost.
At this point I was fresh out of ideas and did what many a product developer does -- put the design on the back burner and move onto other things. I gave myself a rest and let ideas continue to percolate through my subconscious.
The cube design came to the surface again when I was looking at 2mm male pin headers for something else. I was specifically looking at headers with 2 rows of pins instead of just a single row of pins. While looking at the mechanical drawing of a header I noticed something. The space between the two pin rows, with the width of the pins subtracted, was just a bit bigger than the width of a .062" PCB.
Out came the sketchpad again and I came up with this:
The thickness of the PCB plus the added thickness of the copper plating *should* fit between the rows of the 2mm header. This was using the header in a non-standard way and would require hand soldering. But, some soldering is OK in an electronic kit and this was easy soldering.
I had some old .062 circuit boards lying around and could measure their finished thickness using calipers. It looked very promising
I scrounged some 2mm 2 row headers and viola'! Fits beautifully.
Another trip to Digi-Key found 2 row male headers, 2mm spacing, unshrouded, 2 rows, 4 pins, pre-cut to size = $.31 qty 1, and $.145 qty 1000.
Note: Digi-Key and Mouser are your best friends when developing products.
If I used the original horizontal LED board plugging into vertical PCBs, then I'd need 128 of these connectors per cube = $18.60. I’ve cut the connector cost in half, which is nice and all, but I was back to needing three unique circuit board types: vertical, horizontal, and base.