I've decided on a new working title for the touch controller project: "Stribe"
1) the name "xenome" is pretty much taken by a pharmaceutical company
2) "xenome" is a little too close to "monome"
Stribe means "stripe" in Danish. I like that it sounds like "scribe," and "strive," and that it doesn't mean anything particular in English. I think there's a shoe somewhere called this, and an athelete with it as a last name, but otherwise it seems unused. And who knows, maybe I'm part Danish.
Stribe nee Xenome time-lapse progress pics:
paper sketch + actual parts for comparison
breadboarding the MAX7221 + bar-graphs + Arduino
6 Spectrasymbol "hotpots" on top of stacked bargraphs. This showed that putting the pots right on top of the led bars is a bad idea for 2 reasons: 1) you can feel the joints between the bargraphs, 2) air bubbles appear between the uneven bargraphs and the sticker surface
These are 2 led boards. I designed the circuit layout in ExpressPCB and 3 days later they appeared in my mailbox.
I learned that I'd made the though holes around the edge too small for the pin headers I had planned to use. fortunately, the female headers fit. I had to file the edges of each header to get them to fit right up next to each other.
Here's the bottom of the assembled led board. That's uh, lessee, 2240 solder joints for the leds, plus 280 more for the pin headers. Went a bit cross-eyed. Learned there needs to be a bit more room between the led segments - but maybe that's because these are cheap. The board ended up slightly curved from the ceramic cases snugged right up against eachother. Higher quality parts might work better. Also, it was very fiddly getting the tiny legs of each bargraph to line up and go through the small holes. I don't have much room to make the holes a lot bigger but the higher quality name-brand bar-grpahs have thicker legs so I'll need to open these up a bit, too. One thought was to use IC sockets in place of all of the actual bar graphs, then insert the bar-graphs into the sockets. This would ease assembly as well as allow easy swap out for different colors or to replace a bad unit.
Here's the top of the assembled led board. I added a sheet of plastic cut from a paper binder - sticking the sensors onto this will make for a much smoother surface. Ideally, it would be great if the leds were all one piece, like little SMD leds embedded into a thin piece of plastic.
Here's the clear "softpots," installed. I was leaning away from these clear ones because the tactile feel of them isn't as nice as the yellow "hotpots" - but I realized I can put another layer over the softpots and they will still work. Which is great because now I can find a surface that has the touch and look I want - e.g. translucent, transparent, with different textures, possibly ridges or grooves to demarcate each stripe... not to mention that I could print stuff onto this layer. This layer could have different designs on it to provide help for different apps.
It's also good that I waited to finalize the circuit for the driver board. Now I see where I can include routing for the strips right on the driver board.