DataHand questions - designing a keyboard with a finger trough

[Zekromtor]

lol, I had no idea. Thank you for letting me know and sorry about all the rambling nonsense that came from my misunderstanding. Stickies could actually be very convenient now that I know how it works... I have some thinking to do.

*ignore the crap I redacted from this original post, I went back and reread your layer locking desc*

And damn, that's a good price on the Matias keys. It costs me more to make my own. I really like that company.

[wolfv]

Zekromtor,
No worries.  I have been studying keyboards for a year and am still learning.

I like the idea of tactile leaf spring switches and .75x1 keycaps on the home row.

[wolfv]

I am making a list of parts to make the new keyboard and could use some advice on switches for the fingernail row (activated by extending fingers).

Tim Tyler made an entire keyboard with low-force snap-action Saia-Burgess G3 microswitches:
http://mykeyboard.co.uk/microswitches/
The key board can be seen here:
http://mykeyboard.co.uk/microswitch/

But the Saia-Burgess G3 are nowhere to be found.
Probably because Honeywell Acquired Saia-Burgess Controls from Hong Kong-based Johnson Electric 10/24/2012.
So I am looking at alternative switches.

The Cherry E23-90NX Light Force looks promising.

http://www.mouser.com/ds/2/71/E21_Series-187037.pdf
Switch characteristics:
   Max. Operating Force   22    gf
   Maximum Pre-Travel    3.18 mm  (Cherry MX is 2.0 mm)
   Movement Differential    0.76 mm

Cherry keycaps can be glued onto the nub on the end of the lever.

I am open to ideas.
Is there a way to make a Cherry MX with about 20gf?

Thank you.

[OldDataHands]

https://github.com/dodohand/dodohand

the part of the finger switch assembly
that you're interested in having
could be extracted and used alone.

looking forward to what you come up with!

[wolfv]

OldDataHands,

Thank you for the suggestion.
A magnetic switches would have the best feel (not that I have ever touched a DataHand).
I was hoping to avoid the effort of developing a magnetic switch.
Building from your DodoHand work would significantly cut development time.

Here is a stupid question I had since reading the DataHand patent.
Why does DataHand use an optical switch and not a magnetic switch something like this?:
   Two ferrous contacts on the base
   A conductive magnet on a lever
   The magnet normally closes the circuit.
   Pushing the lever opens the switch
Without optic switches, cordless keyboard would be practical.
UPDATE/ANSWER: the lever moves slowly so contact points would get pitted.

BTW Your DodoHand is an awesome project.

[wolfv]

I am still looking at switch ideas for the fingernail row (activated by extending fingers).

Here is a picture of a snap-action switch with the cover removed:

The red part in the picture is a what they call a "plunger"; it moves the switch's contact.
The plunger hole has a rectangular cross section of 2.8mm x 4.2mm.
I am considering replacing the plunger with a 3D-printed plunger that has a built-in keycap.
Maybe ShapeWays' White Nylon.
How durable would a 3D-printed plunger be?

[wolfv]

Here is another idea.

Snap action switches can be purchased with flat metal levers.

Shapeways could 3D-print keycaps that slip over the end of the lever.

But the switch would be mounted at a slightly up-side down angle.
When a snap action switch is held up-side down, does the lever stay in contact with plunger or is there a small gap between the lever and plunger?
Could the lever be bent to reduce pre-travel and maintain lever-plunger contact?

I would greatly appreciate it if someone with a loose snap-action switch and lever could answer these questions.  Radio Shack does not have them in local stores.

Thank you.

[Zekromtor]

I have a metal lever switch from radio shack (bought in store, metal bin w/drawers). I added one to my Kinesis but didn't end up using it due to the placement not being great.

It looks exactly like this:



There is no gap between the lever and plunger at any angle. I can shake the thing and not feel any motion anywhere in the switch. You can bend the lever however you want to change the characteristics, you can see the guy did so in the image linked as well.

The switch honestly has a very nice feel to it when naked. Activation pressure at the end of the lever is substantially less than a matias clicky switch, yet still feels a little stiff for activation with an upswing of the finger, but that may just be due to my fingers having no practice with that motion. It also just felt...weird...with a key cap glued on it. Can't explain.

Probably goes without saying, but do not let any flowing glues anywhere near the thing. I tried using super glue to mount some of these, being extremely careful to keep the contact points away from any seams in the plastic, but somehow the glue always managed to prevent the switch from every switching again. Hot glue worked fine.

[wolfv]

Thanks Zekromtor.  That was very helpful .
I will be ordering some sample micro switches to see which one feels best.

[jacobolus]

I think it’s possible to get somewhat the same effect you’re going for here on a flat keyboard by using the right keycap profile. Still probably not as good as a fully sculptured case, but much cheaper to mass produce.

Cf. http://geekhack.org/index.php?topic=62417.0 http://geekhack.org/index.php?topic=62444.0



Or with just a single extra bend, could do something like:

[jacobolus]

www.google.com/patents/US5627566

[jacobolus]

Here’s a good one, though the number and f key rows need to be higher, and since the rows are straight and hands are not, it doesn’t do a very good job of fitting all four fingers.

https://www.google.com/patents/US5469160

[jacobolus]

Check it out:
http://priorart.ip.com/IPCOM/000067608