Are there any unconvertible switches left?

[DMA]

Resistive is solved since forever.
Capacitive - 7 years ago, made easily reproducible 2 years ago.
Inductive - 2 months ago, and I'm pretty sorry I didn't do it a year ago.

Anything else that exists outside HaaTa's collection but not yet convertible?

I'm bored and have some free cycles. If you send it to me - I promise to have a swing on that.

[PlacaFromHell]

I wonder if there is any piezoelectric or acoustic switch out there. You can also work on optical switches but they sure are very boring and easy to convert.

[gipetto]

you've covered most of the electromagnetic spectrum there so unless you want to make a radioactive switch based on a smoke detector circuit or xrays then you're just doomed to rework the same designs. I always wanted to build a keyboard based on spdt switches, because it is possible to make them immune to switch chatter. the spdt switches I have seen for sale though haven't a great feel or are too deep, suffering from the same issue as beam spring modules.

There probably is room for improvement in switch matrixes, for instance to see if it would be possible to achieve n key rollover without per key diodes. Off the top of my head, maybe put an isolation transformer on each column or a design based on a time domain reflectometer.

[Findecanor]

There are some weird patents in the Wiki about rollover that remind me of what you write.
Microsoft Sidewinder X4 also had increased rollover using resistors, and those could be printed on a membrane.

Cherry is also supposed to use some kind of magic with their "Real Key" sensing in the MX-Board 6.0, and that is still a mystery, to me at least.

[Sangdrax]

The old Hall Effects (pulse vs hold) are not hammered out yet IIRC. New Hall Effects are made and they are understood but there is no basic conversion process for the old boards. This is as far as anyone has gotten fullsize I think viewtopic.php?f=7&t=21908

I got an NOS Microswitch board module I'll give you to tinker with if you like. It came in like two days after you got to visit. Might be a fun project to see if you can convert with CommonSense.

[gipetto]

>There are some weird patents in the Wiki about rollover that remind me of what you write.
Microsoft Sidewinder X4 also had increased rollover using resistors, and tho

That was an interesting read, thanks. Well the microsoft rep admitted that their tech works by putting a resistor at each switch to achieve n-key rollover. the model f acheives the same by putting a capacitor in each switch, and your average mx gaming keyboard does it by putting a diode at each switch. I figure it may be possible to design a low cost keyboard with a pcb trace inductor in series with each mx switch. by measuring the inductance of each key press it may be possible to eliminate ghost keys, but that could slow latency.

[JBert]

>There are some weird patents in the Wiki about rollover that remind me of what you write.
Microsoft Sidewinder X4 also had increased rollover using resistors, and tho

That was an interesting read, thanks. Well the microsoft rep admitted that their tech works by putting a resistor at each switch to achieve n-key rollover. the model f acheives the same by putting a capacitor in each switch, and your average mx gaming keyboard does it by putting a diode at each switch. I figure it may be possible to design a low cost keyboard with a pcb trace inductor in series with each mx switch. by measuring the inductance of each key press it may be possible to eliminate ghost keys, but that could slow latency.

The Sidewinder design might be the cheapest you're going to get. The resistor is printed as part of the membrane, so at worst the membrane needs to go through a few "stages of printing" depending on whether it's printing conductive traces or resistors. But that's nowhere near the sort of process you need where components are placed on a big keyboard PCB.

The only downside of the technology was that it couldn't drive a big matrix IIRC, meaning that the keyboard is actually split in a number of zones. As a result, you need more wires from all the zones to the controller, and that might drive up price again. It's still the most interesting bit of innovation in rubber dome keyboards though.

[ZedTheMan]

Seconding the old hall effect switches of different varieties.

[Findecanor]

BTW, you could use diodes with a membrane: you would just have to route each switch to a bigger PCB, and have diodes on that. The connector could be.. an edge connector with pressure from foam, so no cost there. Then the diodes could be integrated diode-banks that may be cheaper to place in bulk.
There are a few keyboard models that do that.

[XMIT]

I'd like to experiment with strobing power to a "pulse" type Hall sensor. It's on my long list of things to get to.

Previous work: viewtopic.php?t=12379

[Slom]

I'm not sure how much sense it makes to talk about switches as opposed to keyboards when it comes to conversion.

There *are* converted Hall Effect keyboard. And some keyboards use both "pulse" (for alphas, to avoid rollover issues*) and "hold" switches (for mods), which reinforces my first point.

* by not detecting held keys, you dont have issues** with multiple keys held at the same time
** unless you are a gamer

[DMA]

So it's completely covered then.
Awesome!