Interesting read, probably nothing new...

[Lammie]

http://blog.amarsagoo.info/2008/05/science-of-keyboard-design.html

[dorkvader]

interesting, but so far, I think he's incorrect about apple scissor keyboards not having hysterisis. It's a bit different for domes, as everythign happens at the bottom, but the dome compresses at bottomout somewhat, causing some measure of hysterisis. I thing it;s just not beign properly debounced on teh controller side, but it's hard to say for sure.

will keep readinga fter my meetign

[tp4tissue]

there would always be hysterisis assuming you're pressing the key hard enough to compress the rubber during bottom out..


hysterisis is not a physical implementation only, it's also software side.. how long before the pc starts to repeat input.


i think if the article dude, is saying he's getting double inputs on the bottoming out rubber dome , it's because when the dome hits the bottom, it sticks After debounce, and because rubber domes naturally causes people to Press-n-hold to ensure keystroke input, there's a higher likelyhood that youi get repeat key.

[damorgue]

I would argue that there is NO hysteresis. You mention that you can depress it further past the actuation point, which is absolutely irrelevant. Hysteresis would be the difference in point of activation and deactivation which would be zero in a rubberdome, no? If you press it 2mm, and it activates after 1mm, then release it and it deactivates after 1mm, then the two points coincide and it doesn't matter that you can depress it past the activation point (1mm in this case).

[tp4tissue]

I would argue that there is NO hysteresis. You mention that you can depress it further past the actuation point, which is absolutely irrelevant. Hysteresis would be the difference in point of activation and deactivation which would be zero in a rubberdome, no? If you press it 2mm, and it activates after 1mm, then release it and it deactivates after 1mm, then the two points coincide and it doesn't matter that you can depress it past the activation point (1mm in this case).

No, I'm saying the debounce + repeat key delay timing = the action of physical hysterisis.


the compression at the bottom can be thought of as having engaged in physical hysterisis because of the initial debounce.

[dorkvader]

I would argue that there is NO hysteresis. You mention that you can depress it further past the actuation point, which is absolutely irrelevant. Hysteresis would be the difference in point of activation and deactivation which would be zero in a rubberdome, no? If you press it 2mm, and it activates after 1mm, then release it and it deactivates after 1mm, then the two points coincide and it doesn't matter that you can depress it past the activation point (1mm in this case).

Actually, I think you are absolutely correct about that. I'm not sure what I was thinking, other than that the behaviour described seems to be more of a less-effective debounce than hysteresis.

@TP4: I don;t think that debounce + repeat delay timing = hysteresis. They may serve a similar purpose (to keep out unwanted multiple registrations) but hysteresis has to do with the physical location of the switch along its travel, which is not addressed here.

Microswitch hall effect sensors accomplish this with a schmitt trigger, which is even a different implementation and a little more complex than say the hysteresis of an MX blue.

edit: awesome quote:

The Handbook of HCI recommends key travel to be between 1.3 and 6.4 mm, and the key force to be between 28 and 142 g

That's a very narrow range, I'm not sure if any keyboard meet that [/sarcasm]


---
Reading the comments, I notice Damien [)amien from GH here posted back in 2008!

[jacobolus]

This particular blog post is just a summary of a famous book chapter based on some famous much older documents (and various research papers over a few decades) that have been linked from various geekhack discussions several times. (Frankly I don’t think it’s the most useful; though it does mention a bunch of important factors in keyboard design, it doesn’t really provide too many useful design criteria/suggestions.) In general, research papers I’ve found on keyboard design are very unsatisfying, coming with poor statistical analysis, or tiny sample sizes, or much too limited study lengths, or not testing the most important (IMO) variables.

http://my.safaribooksonline.com/book/electrical-engineering/computer-engineering/9780444818621/part-viii-input-devices-and-design-of-work-stations/1311#X2ludGVybmFsX0J2ZGVwRmxhc2hSZWFkZXI/eG1saWQ9OTc4MDQ0NDgxODYyMS8xMjg1

* * *

Here are some Geekhack threads to check out:
http://geekhack.org/index.php?topic=55099.0
http://geekhack.org/index.php?topic=54624.0

* * *

But do note, Amar Sagoo is the creator of Tofu, which is still far and away the best way to read long text (essays, papers, books) on a computer screen. I don’t know if there’s anything like it available for touchscreen tablets, but there should be.

http://amarsagoo.info/tofu/