These are some little experiments with backlighting Matias switches. I tried two general approaches: ordinary through-hole 3mm LEDs, pointing up under the switch, and reverse-mount SMD LEDs, which mount on the back surface of a PCB and point up. The idea of a single-key switch was inspired by the
Enabler by Melvang & MOZ, and the
Amoeba by mtl, and I'm definitely not the first person who thought of shining an LED through a hole in the PCB for lighting Matias switches (e.g.
here). While those single-key PCBs both support Cherry switches, that had to be sacrificed on mine to allow SMD backlighting.
parts supported:
- any Alps-compatible switches (but no point in backlighting switches that aren't translucent)
- through hole, 0805, or 0603 resistors
- through hole or 1206 reverse-mount LEDs
- through hole, SOD80, SOD123, or SOD323 diodes
The through-hole LED idea takes up about an extra 7mm from the bottom of the PCB, which is probably impractical for any real keyboard, but the reverse-mount LEDs work well and big enough to be easy to solder by hand or by solder paste/hot plate.
The exact LEDs I used are LTST-C230KRKT since they're available from common distributors and are pretty cheap (less than $0.10 @ 100u, less than $0.05 @ 3000u). The datasheet says you should make a square hole for them, but I used highly advanced mathematics (or, uh, basic geometry) to just pick a circular hole size that could be drilled instead.
what's next?
This is my first PCB, so unsurprisingly I messed up some of the silk labels and swapped around some of the SMD pads. The next version will be slightly smaller to fit through Alps-sized plate cutouts easily and will remove the through-hole LED option.
I might (very small chance) be willing to do a group buy, with a cheap chinese board house these could be made for like $0.10 @ 5000u, but the tax/liability stuff makes me a little uneasy.
Sadly, there are no readily available transparent/translucent Alps-compatible keycaps, no backlit Matias boards, etc., but maybe this can convince someone to make some. My main goal here is mostly to inspire other people to do more work :P
