Things are really going now. I’m collaborating with K, who is amazing. She can sew, which is so far beyond my capabilities I can’t even imagine how it works. And she can do good design, and seems to have a real appreciation for straight lines. I think we’re a good team.

Meanwhile back in the design, I’m struggling to solve the power problem. In short: we need a lot of power for the 200 LEDs, something like 200 @ 60 mA = 12A. That’s a *lot* to put through the LED strand. It would melt. So we need to supply power at low amps to small chunks of strands.

I had a good convo with Adafruit who sold me the first strand. Upshot: they find that lots of the LEDs bought from China are faulty, lots of testing is required, so they think it’s worth it to sell at $1.65/pixel (i.e., $40 for a strand of 25 pixels) instead of the $0.95 Boz’s Shenzhen supplier allegedly had (we never got the link so I don’t know).

The strands are 78″ stretched out. The LEDs are bigger than I expected, nearly the thickness of my index finger. Of course, 12mm, I should have realized.

Thus my sense of the topography is changing. I’m going to spend the money to get the 25-LED strands from Adafruit because this gives us a bunch of flexibility.

Still trying to figure out how many battery packs we want. Smaller packs are lighter, could be distributed around the coat, but will be a huge PITA to charge.

And then there’s the voltage problem. The batteries will provide 7-9v (depending on how I set them up). The LEDs want 5v. How to step down? A little regulator for each strand, or a big regulator for the whole power bus? Given the power efficiency needs, a simple LM7805 regulator would lose so much in heat it won’t work. I feel like keeping the voltage high to the last point would be more efficient, too. Hmm, unsolved problem.