In continuing my trend of putting RGBWUV and my MELD UI in every light possible, I got a hold of the discontinued Nitecore EX11, which uses piston drive (which I love and have worked with before). I wanted to fit the full MELD2 driver into it, but there is just not enough room in the pill with the piston drive mechanism. I ended up designing a custom board stack that gets rid of all the inductive converters and just uses AMC7135 regulators (1 per color channel, 3 for white). This means the light is restricted to rechargeable cells, unfortunately.
The daughter board actually came so close to the wall of the pill that I had to notch it out to pass wires through from the main board. The entire thing is run by the same PIC16F1825 as regular MELD boards, and it runs the same firmware (with a compile option for linear lights, which makes a few slight changes).
Here's the schematic for the main board:
And the daughter:
Four connections go between main and daughter board. The main board has the positive battery contact and the contact ring for the piston. Since my total available height was very small, I intentionally aligned the regulator on the bottom of the daughter to sit above the PIC, which is shorter than the regulators on the main board. This lets them stack together into a pretty short assembly:
Here's the pill completed, and an XML color wired up for electrical test:
The other challenge with this light is that the reflector opening wasn't big enough to fit a MELD LED board. I didn't want to ruin it by drilling it out, so I went back to a crazy technique I've used before of mounting the color LEDs around the reflector in individual holes. This process started with wiring them up in mid-air:
I then drilled four holes evenly spaced around the reflector, about midway up. Then to reduce the depth to get the LEDs farther out, I filed down around the holes until the wall was about a millimeter thick. I carefully arranged the LEDs and the wires to get the LEDs centered in the holes, and glued them down with thermal epoxy. This was a painstaking process because I had to hold the LEDs in place while the epoxy cured, and I had to do it four separate times so that the epoxy was facing up and wouldn't drip down.
Here's the result:
And the back of the driver:
It all turned out great, although the color beam patterns are terrible, as expected. The white beam is perfect, and isn't noticeably affected by the color emitters.