Reverse Rubber Dome Switch?

snerual · 25 Mar 2011, 21:03

I know, I know, this title doesn't make much sense. I came across an interesting board today. It has plate mounted 'switches', but none that I've ever seen before. I have various ALPS, Cherry and many Buckling Spring boards, but these are very unusual and different.

The key caps have a rubber dome inside. The cap clicks onto the stem on the switch and the rubber dome pushes the cap up. Push it down and the switch makes contact. Release it and the rubber dome pushes the cap up again. It feels like a rubber dome and looks and works much like a regular rubber dome board, so why are these things plate mounted? Any idea what these are? If intrigued enough I may just buy the board for $10 and experiment with it a bit.

gore · 25 Mar 2011, 23:05

I think the IBM SureOne's had a similar thing with rubber domes in the caps.

sixty · 25 Mar 2011, 23:07

Interesting switch. Never seen it before either. Looks like an easy-to-service rubber dome for industrial use.

daedalus · 25 Mar 2011, 23:20

Looks like a rubber sleeve switch with a rather fancy contact mechanism.

I'm interested by the white slider. What is it actually doing? Does it push upwards by itself?

snerual · 25 Mar 2011, 23:48

OK, so I bought the board for $10. Very heavy! It's an industrial board made by Devlin in the UK. Seems to have been used in the printing industry. I'll make sure to post some more pictures later.

The white slider is down by default (no spring inside the switch). The rubber dome in the keycap basically keeps it up. Another interesting fact is that the Caps Lock, Num Lock and Scroll Lock keys have red LED's in the switch and round windows in the caps.

snerual · 26 Mar 2011, 00:13

The board:

The back is metal:

Some interesting keys:

Scroll Lock key with LED window:

snerual · 26 Mar 2011, 00:18

Same Scroll Lock key with case taken off. Note the red LED top right:

More swtiches. Note the rubber dome inside the green cap:

Devlin controller:

View of the PCB though the (dirty!) metal plate around the arrow keys:

snerual · 26 Mar 2011, 00:37

Last image - a closeup of the switch:

webwit · 26 Mar 2011, 00:54

I bet it is some old Omron, C&K, Apem or Alps industrial switch.

sixty · 26 Mar 2011, 01:04

1998... I think its too new to be some obscure old switch.

webwit · 26 Mar 2011, 01:23

Could still be some kind of out of fashion industrial rubber dome. It seems too complicated for a consumer rubber dome from some Taiwanese producer. On the other hand it is an open design. I've seen those rubber caps underneath the keycaps before, but threw out the keyboards carrying them. I think they were Compaqs. Maybe Honeywell.

snerual · 26 Mar 2011, 01:31

I also remember seeing an older HP or Compaq with rubber caps under the keys. But otherwise that was a fairly regular rubber dome board.

Devlin seems to use this as one of their standard case designs. The similar KMX-144 (with Cherry MX) on GH here: http://geekhack.org/showwiki.php?title=Island:12294

Guess I can always contact Devlin to find out more about these switches. As far as I'm concerned they're not all that nice to type on. The board is PS/2, but I have not hooked it up yet, so I don't even know if it works at all. Should also be interesting to see if I can get the additional function keys to work.

webwit · 26 Mar 2011, 01:38

Considering that the rubber cap is round but the open areas on the switch are not, maybe that is unrelated to the switch and something Devlin added. Perhaps it some kind of standard dust/sound condom.

snerual · 26 Mar 2011, 02:09

No, remove the rubber cap and the switch won't work. The switch itself has no spring, so the white stem is down/activated once you pull the cap off. Remove the rubber from the cap and the key is always pressed. The rubber basically acts as the 'spring' that lifts the stem. It's all very strange and intriguing.

webwit · 26 Mar 2011, 02:31

Ah ok, now I understand. Well, the technical part of it

snerual · 26 Mar 2011, 02:52

Yeah, TU Delft certainly never prepared me for anything like this. Perhaps a degree in 'Keyswitch Engineering' would have been more helpful. Of course that still wouldn't help me much here in Canada - "Are you a Mechanical or Civil engineer?", "Both. I'm a very civil mechanical keyswitch engineer".

hoggy · 26 Mar 2011, 14:46

I've got a cherry mx switch version of this board. The keycaps on yours are much nicer, though.

http://geekhack.org/showwiki.php?title=Island:12294

ripster · 26 Mar 2011, 15:44

To put it another way It's a BRS (Buckling Rubber Sleeve) variation like the M4-1 but with sliders instead of a peg to close the switch.

Findecanor · 26 Mar 2011, 18:13

Foam-and-foil capacitative keyboards often have buckling rubber sleeves like these, if they don't have springs. The foam makes the keys very mushy, though, but allow actuation to happen half-way.

Specter_57 · 16 Feb 2012, 05:15

..

I have five of these exact same boards, same down to the colors and legends..same switch under-cap profile...everything, the same....and likely picked up from the same vendor (In Toronto...?)

Those switches are *magnetic hall-type switches*....apparantly unusual in the keyboard world.

.............
Spec57

Tycn · 16 Feb 2012, 14:41

Nice looking keycaps too. Dye sublimated PBT?

Specter_57 · 18 Feb 2012, 00:29

..

Dye sub? No idea on that, sorry.

I have a thread over on Geekhack on my boards along with some info that was contributed and dug up on them.

Look under "Great Finds" and then the "Devlin KMX-144 find - Thread Reload" thread.

................
Spec57

XMIT · 08 Apr 2015, 20:17

(wow, necro from 2012.)

These are magnetic valve switches. The ferrite bead by the center of the key stem is a dead giveaway. The sliders all contain a tiny magnet. When you push down a key it moves a magnet in front of the ferrite bead. This temporarily magnetizes the bead and prevents it from being able to induce current. Very clever.

See: http://deskthority.net/wiki/ITW_magnetic_valve