[Arm-netbook] Future case idea: subnotebook/PDA with QWERTY keyboard

[Paul Boddie]

On Sunday 4. September 2016 18.50.53 Joseph Honold wrote:
> 
> My idea is to use snap domes attached to a sticker and placed directly on
> the pcb which has exposed copper pads for contacts (keyboard matrix). The
> sticker could be laser (or hand) cut to any shape and snap domes hand
> placed (for prototype). The snap dome method is how most phones (and Zipit
> Z2, see my post https://mozzwald.com/articles/zipit-soft-keypad-mod) do it
> these days. The snap domes are available and I actually got a sample kit
> from Snaptron (http://www.snaptron.com). There are some far east
> manufacturers of snap domes also.

For reference, here are some pictures of the originally-planned successor to 
the Ben NanoNote that show what you're talking about:

http://en.qi-hardware.com/wiki/File:AVT2_RC1_keys.jpg

(The circuit boards, employing fairly simple contacts for domes as opposed to 
the oft-seen elaborate patterns that are potentially more suitable for coated-
silicone keymats/overlays, as far as I can tell.)

http://en.qi-hardware.com/wiki/File:AVT2_v1.0_works.jpg

(The "dome sheet" applied to the board.)

Somewhere on that site is a picture of the "dome sheets" being applied by 
assembly line workers, but I can't find it at the moment.

> The difficult part (IMO) is creating the rubber/silicone overlay. A
> prototype could be made by either 3D printing a mold and casting a
> silicone keypad, or just 3D print the keys in plastic (or some other
> preferably soft material). Both these methods should work but I don't
> expect backlight to work well if at all (need translucent material). The
> labeling of keys might be difficult to achieve with 3d printng.

Overlay/keymat production seems quite specialised, but maybe people here know 
a bit more about it.

> Before I found out about EOMA68 I was intending to make a raspi handheld
> using this keypad layout
> https://mozzwald.com/public/images/misc/keypad.png
> 
> Are there any preferred keypad layouts?

That's asking for trouble! One thing I wouldn't mind knowing is how decent 
space bars are done using domes. Do they really involve multiple domes, or are 
there elongated ones that do this job?

Paul