geekhack
geekhack Projects => Making Stuff Together! => Topic started by: cy384 on Mon, 04 January 2016, 20:01:17
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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 (https://geekhack.org/index.php?topic=55744.0), and the Amoeba by mtl (http://deskthority.net/workshop-f7/another-single-switch-circuit-board-t11420.html), 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 (https://www.reddit.com/r/MechanicalKeyboards/comments/37nfmg/planck_all_finished/cro7848)). While those single-key PCBs both support Cherry switches, that had to be sacrificed on mine to allow SMD backlighting.
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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
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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
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oh I love it. I tried doing a few backlit keys with the enablers on mx switches using through hole parts and it was not really designed for that clearly lol
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Found this the other day, http://imgur.com/a/JMvav
I think 2x3x4mm LEDs would be much better.
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Found this the other day, http://imgur.com/a/JMvav
I think 2x3x4mm LEDs would be much better.
Yeah, the 3mm round LED idea didn't turn out great. Putting rectangular ones on their side works nicely with PCBs that support both Alps and Cherry switches. Though I wonder if there are LEDs in that size that only shine from one side, rather than in all directions, since a lot of that doesn't go through the hole.
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Yes, there are, side lens or side something is the magic word, search for them in DIgikey or Mouser, they have them, at least in SMD footprints they exist.
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Designed another, smaller version, it's now 14.12x11.30mm, which is small enough to fit through an alps-sized plate hole. Dropped the through-hole LED option, added some little markers for wiring directions. It seems like a finished design, I haven't thought up any particular changes in the past few weeks. I do have some ideas that go in a completely different direction, I'll post those as I work on them.
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cool stuff