geekhack
geekhack Community => Keyboards => Topic started by: agbiotec on Mon, 21 December 2009, 11:46:15
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Looking at these beautiful keyboards here,
http://www.9999hp.net/keyboard/temp/
I saw the term "Membrane buckling spring". I think I know what capacitive buckling
spring is (click,click Model M or CLICK,CLICK for Unicomp's), but what's up with this ?
Does it have a dumper or something ? Anyone has links to pics please send over...
Also, I might be hallucinating, but my rubber dome Blue logo IBM model M (1995) seems like it has a bit of tactile feedback... anyone seeing similar ghosts ?
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M and unicomp are both membrane BS, the F is capacitive BS
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The basic idea behind both is the same except for the type of mechanism used to detect whether the buckling spring mechanism has been actuated. In the capacitive design, the spring pivots forward a hammer which forms a capacitor between two electrical contacts. In the membrane design, the hammer strikes a membrane similar to that of a normal rubber dome keyboard.
On paper, the underlying mechanism wont affect the user's experience. In reality, the two mechanisms require different hammers which in turn require different springs. The different springs have quite an impact on the tactility and noise of the keyboard. Most (if not all really) who have tried both will say that the capacitive design is superior in terms of tactile and auditory feedback. Problem is that they are harder to find, and the Model F PC/AT keyboard pictured in that link you posted is the only capacitive keyboard that can readily work with a modern PC. As pointed out above, the IBM/Lexmark/Unicomp Model Ms (except for the rubber dome variants) have membrane BS mechanisms.
I really need to start that keyswitch section in the IBM wiki...
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and topre has domes but no membrane
so what is the easy way to rag on a dome+membrane board?
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This is why nobody should ever refer to "rubber domes" as "membranes" - while true, it confuses people.
The membrane in a Model M is the combination of two plastic sheets that get pressed together in key areas when a key is pressed (simplified explanation, but all that is relevant). All rubber dome keyboards have a membrane...however, people start referring to the sheet of actual domes as the membrane, which is not correct. The domes are the domes, the membrane is the membrane lol
and topre has domes but no membrane
so what is the easy way to rag on a dome+membrane board?
Yeah, the distinction between contact mechanisms and keyswitch mechanisms is understandably confusing to many newcomers. A common variation on this is when people think that the Model F is some kind of Topre keyboard because it's 'capacitive'
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I'm gathering up the ingredients for RetroBrite for my SGI granite and just need Xanthan Gum. Sounds like Star Wars Bantha Fodder.
I don't think the choice of thickener would be terribly critical. You can try starch fluor if you have some handy.
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Even when it comes to resistive contact type switches, not all rubber dome boards use membranes. IIRC, some use carbon buttons in the domes which bridge two contacts on a PCB.
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I think chimera15's latest wireless minihack is based on such a PCB...