geekhack
geekhack Projects => Making Stuff Together! => Topic started by: epicepee on Mon, 20 October 2014, 15:48:33
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Most keyboards use their PCBs to keep the switches (Cherry MX) in place. So how does one do it without a PCB?
MX switches do have those little tab things, but they seem pretty weak compared the the force required to pull a keycap. They also require a 1.5mm plate, which is thinner than would be ideal for a stiff backplate. Similarly, some people use hot glue, but I can imagine that breaking quite easily as well.
What do most people do to hold their switches in?
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Plates work well enough, 1.5mm is fine for aluminum and steel materials.
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properly sized plate holes should result in a firm hold on the switch. I imagine Cherry did a fair amount of testing on their switch design to ensure that the switch firmly holds onto a properly sized plate. Hot glue, as you mention, is a popular method for adding a bit of hold, and can be rather strong. Don't underestimate it.
As for other methods, you could shim the switch holes to make the fit tighter, say with plastic wrap or tape. Just don't break the switch trying to get it in a hole that is too small.
How solid your plate is depends on the material, and how many points of connection there are between the plate and the back of the keyboard. More connections from back to plate will result in a stiffer, more solid plate. How many connections you really need, or you can fit, will depend on layout. Using something like steel for your plate, even at 1.5mm thick, is plenty strong for a plate. The key thing to remember about plates is that they are only part of the main source of strength of a keyboard. They hold the switches in place, and add stiffness. The plate, however, relies on the casing/back of the keyboard to strengthen it.
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The laws of physics.
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without a PCB it is possible to pull a switch out of a plate when changing keycaps. I think glue is recommended to ensure they stay put for direct-wired designs.
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Would a 1.5mm 60% steel plate be strong enough if it were anchored only at the top, bottom, and sides? Adding supports between keys would really screw up my design...
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Would a 1.5mm 60% steel plate be strong enough if it were anchored only at the top, bottom, and sides? Adding supports between keys would really screw up my design...
I've been working with 1.5mm aluminum over the past week or so and I don't think I could bend it with my bare hands if I tried. I don't plan on adding any support (it's going to be like a Gons keyboard) and I think it will be just fine.
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Would a 1.5mm 60% steel plate be strong enough if it were anchored only at the top, bottom, and sides? Adding supports between keys would really screw up my design...
The plate will be plenty strong enough anchored just at the top and bottom, you can anchor at the sides too if you want.
The issue is that without a PCB, it's possible to pull the switches out of the plate when you're changing keycaps. I recommend either being really careful when changing caps or gluing the switches in place.
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Just don’t change keycaps. Problem solved. :)
(But actually, Cherry MX caps all come off pretty easy; it’s certain types of Alps caps that you really don’t want to change when the switches aren’t soldered down to anything substantial.)
1.5mm steel or aluminum is more than rigid and sturdy enough. 1.5mm acrylic gets a bit iffy, so for folks using acrylic and direct wiring I recommend using 2 layers: one that’s 1.5mm (or maybe 1/16") thick for the switches to clip to, with another layer underneath (holes cut slightly bigger) that’s thicker, maybe 5mm+ (or 1/4"+).
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New Cherry MX switches in a 1.5 mm steel plate with square hole should hold well enough.
Otherwise you can try what I did:
http://deskthority.net/workshop-f7/katy-keyboard-or-k80cs-key80-contoured-split-t8524.html#p181273
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I use hot glue to help keep them in position. I still pull one out the plate now and then when changing caps, though, since the little tabs on some of my switches are worn away and Clear stem hold onto caps with a vengeance.
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Just don’t change keycaps. Problem solved. :)
(But actually, Cherry MX caps all come off pretty easy; it’s certain types of Alps caps that you really don’t want to change when the switches aren’t soldered down to anything substantial.)
SP DSA keycaps with the "other" stem type are particularly difficult over clears. In many keyboards with removable keytops you will pull the keyswitch in half, then go find the spring, then pull the stem out of the keycap with a pliars. Alps are notorious, but cherry MX have their issues sometimes too. The easiest to remove I think are probably cherry POM and imsto PBT.
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