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Comment by jstanley | Hacker News Reader

Thanks, I will keep an eye on this. Do you reckon gold plating would suffice or is it likely to get worn away?

Gold electroplating can utilize some relatively nasty chemicals such as cyanide and cobalt but some ways are more safe than others. You could more easily and inexpensively nickel plate it with household materials (and a nickel plating layer is often used as a flash layer for gold plating anyway.)

Simply tinning the copper with solder would likely be the easiest option although I couldn't say how durable that would be against contact wear over very long periods of time. I'd suspect just as durable as nickel or gold plating would be...

I wasn't suggesting I'd gold plate it myself, I meant I could just buy gold-plated wire, as long as it would be sufficiently durable.

Yes, hard gold plating is pretty durable. Take a look at the plating on PCIe card and DIMM contacts. Or just about any high quality connector.

Switches have an advantage over these connectors in that they touch rather than slide. So wear and tear is much less of a problem.

Gold plating wont cut it. It is a very thin layer of gold around the copper and it would wear out pretty fast. I'd recommend bronze.

Might give more flexibility to move to optical sensing and avoid the contact issue entirely.

It would. I think a common option is to use magnets and hall effect sensors. If you use an analogue hall sensor, you can even make an "analogue" switch that can have a different effect if you push it just a little bit compared to pressing it the whole way down.

Neither of these satisfy me, because in my eyes if you're using an off-the-shelf sensor of some kind, you're not really making a switch, you're just putting a little mechanism around another type of switch. Making the contacts out of cheaply-available material is important to me, although it's hard to really articulate why.

I'm trying to do this from as close to "first principles" as possible.

Would it be hard to make a buckling spring switch? You’d need to use a pre made spring but that does not feel like cheating :). Those switches have a fantastic feedback and sound.

We need to stop at some point though. Do we need to make our own wires? That's surprisingly difficult to achieve.

Considering it's a personal project, one can choose where to stop. Sounds like they've chosen to draw the line at making their own switch mechanism.

Unfortunately, some optical key switch designs may be patent encumbered: https://aimpad.com/patents/

I wouldn’t worry about those ones at least.

I read through the claims of the US patents, and they’re essentially describing “turn the arrow keys into a joystick”. US8717202B1 explicitly limits the mechanism to a light-and-mirror sort of arrangement (thus, optical switches). US8922399B2 is a broadening of the former patent, removing that limitation (which weakens it a lot because it’s not describing a concrete implementation but an abstract idea), and thus I think it would be claiming other forms of analogue switches (e.g. magnetic) too. Either way, there are a number of products on the market that, if would be infringing these patents (unless their manufacturers licensed the patents).

Besides all this, I don’t believe individuals need to worry about patents if they’re doing things for themselves only.

But beyond that, I would be quite happy to ignore the Aimpad patents because the concept was not novel, and prior art exists. https://www.youtube.com/watch?v=gEwDImE0DU4 was in 2012 and I haven’t gone searching any further. Taking the broader ’399: the project in that video is, I believe (I haven’t watched much of it, more just read a few comments about it and skimmed it), prior art for claims 1, 3, 5, 6, 10, 11, 12, and maybe others. For the rest, claim 2 is a supremely obvious extension of claim 1. Claim 4 is obvious and shouldn’t be patentable anyway. Claim 7 is… “what? how else could you possibly do it?”, viz. obvious. Claim 8 is obvious (as in, if such noise is a problem, of course you’re going to do this, it’s been a standard technique on input devices for many, many years). Claim 9 is stupid (“slap the rest of the keyboard on it”). I think there’s a good chance you could get the patents cancelled (that is, without waiting to be sued and getting a court to rule) if you wanted.

(Although I wrote a fair bit of detail here, I’m in no way expert on patents. I’ve just picked up a few things over the years from public news and reading, when related things have interested me. Do not trust my conclusions here to reflect how USPTO, courts, or any other relevant bodies will look on things.)

Thank you for the very detailed and thorough response! I should note that your prior art video uses hall effect sensors instead of an optical mechanism. I've also seen that method used by others on reddit, and remember hearing that it might not be as accurate as optical switches.

Search google for optical keyboard switches, they are easy to 3D print. They have clicky designs and just sliders for quieter operation.

Best to buy gold plated wire off the shelf for your design. Solders nicely as well!

I played with gold electroplating pens but they are nasty.

Gold plating is used a lot in electronics contacts to prevent corrosion, it's a pretty proven method that should work just fine without wearing away easily. As far as I understand it, the gold chemically bonds to the metal it coats, so it's not easy to wear it away.

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