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New Trackball Design for easier installation
Howard_Casto:
--- Quote from: RandyT on February 08, 2020, 01:09:57 pm ---I just stumbled upon this. This is a concept I played with about 8 years ago. Even bought a big box of bearings for eventual production. Still trying to figure out what to do with them :).
While this is a very nice and well-thought out package design, it's exactly how a PC optical trackball works, in a different form-factor. They use nylon bearings however, as free-spin is usually not necessary or even desirable in that application.
The issue I ran into, and was mentioned by others, was reliably sensing the surface of the ball for accurate tracking. The older Logitech PC trackballs actually have a special dot pattern on the ball to aid in tracking. I think the newer ones are mixed with mica or other refractive material under a clear outer shell, which indicates some changes had to be made, possibly to support higher resolutions. If a special ball were to be produced with a similar pattern, tracking would work pretty well, at least with slower, non-free-spinning movements. Logitech must have patented the device, but I haven't really looked into it.
However, I went through many iterations of ball types on my prototype, even going as far as sanding and marking a swirled ball with a sharpie to try to get the accuracy close to that of the standard encoder-wheel based units. Some of what I experienced was the usual jitter and skipping one might expect from an optical mouse on an incompatible surface. I will suffice it to say that I didn't feel (at the time) that it was something worth pursuing. That doesn't mean that someone else won't be successful (tracking modules have improved, as things do), but I did put more than just a little time into the project.
In the end, where accuracy is concerned, it probably can't be as good as the encoder wheel variety (at least in this application.) As far as ball movement and feel, you can't really do much better than the 3 bearings design. Unfortunately, I think both will have a tradeoff where a sacrifice will be made in one, for the strengths of the other. But if that doesn't end up being the case, I would love to talk with the person who gets past the hurdles :)
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You bring up some good points. My main concern is about the optical sensor as well. What I've found is that the distance you can be away from the ball while still getting an accurate reading is a very low tolerance. Even with injected molded parts I'm unsure if that could be maintained with a mass-produced unit and that's ignoring the texture issues you bring up. I'm wondering if regular old encoder wheels could be incorporated. Certainly not standard arcade sized ones, but maybe the smaller ones used in a traditional pc-trackball/mouse. They don't necessarily have to be attached to the bearing assembly like on a full-sized trackball, they just need to be free spinning and able to touch the bottom of the ball.
yotsuya:
OP: I have no plans to sell these.
RandyT: Good idea, but I tested this once and it results aren’t there yet.
BYOAC: TAKE MY MONEY NOW !!1!
:cheers:
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RandyT:
--- Quote from: yotsuya on February 10, 2020, 02:18:55 pm ---OP: I have no plans to sell these.
RandyT: Good idea, but I tested this once and it results aren’t there yet.
BYOAC: TAKE MY MONEY NOW !!1!
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:)
--- Quote from: Howard_Casto on February 10, 2020, 02:14:05 pm ---You bring up some good points. My main concern is about the optical sensor as well. What I've found is that the distance you can be away from the ball while still getting an accurate reading is a very low tolerance. Even with injected molded parts I'm unsure if that could be maintained with a mass-produced unit and that's ignoring the texture issues you bring up. I'm wondering if regular old encoder wheels could be incorporated. Certainly not standard arcade sized ones, but maybe the smaller ones used in a traditional pc-trackball/mouse. They don't necessarily have to be attached to the bearing assembly like on a full-sized trackball, they just need to be free spinning and able to touch the bottom of the ball.
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The op's design seems to take that distance into consideration. Once in the "sweet spot" there should be nothing to change the position. Optical mice seem to love a fine mesh pattern, such as that of a good mouse pad. The trick is getting that somewhat accurately onto (or realistically, under) the specular surface of a ball. It can be done, but it would be challenging on a small production scale or where cost is an issue. It might take many expensive prototypes or minimum runs to find a ball which works well enough with a given sensor.
I agree that small encoder wheels would be ideal, but the complexity and therefore cost, will climb pretty rapidly. There's also no real way to do this with transfer bearings, which are the ideal solution for smooth, free and even-resistance movement in all directions. If the ball still rides on a cylindrical surface, there's not much to be gained over the traditional design, other than possibly footprint.
yotsuya:
--- Quote from: RandyT on February 10, 2020, 03:36:20 pm --- If the ball still rides on a cylindrical surface, there's not much to be gained over the traditional design, other than possibly footprint.
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I think it’s the drop-in footprint that has the peanut galley so excited. It’s a cool design, for sure, but I’d rather see it in action and day-to-day use before I spent money for one.
Kudos to the OP for thinking outside the box and using 3D printing for prototyping, though. That’s the way to do it!
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StefanBurger:
Optical Sensors and readability of a curved surface is in fact an issue.
I literally tested dozens of different mouses with mixed results and found just one by incident that turned out to work without any issue.
Strange thing here, is that that particular mouse (ISY IMM 1000) uses the very same IC (A2803) then those mouses who didn't work.
Also there was no difference in the circuit itself.
My best guess is, that there is a difference in optics, either the optical piece/lens or maybe properties of the used LED (wavelength, angle, lumen) that make the difference.
Regards
Stefan
PS: I just ordered another mouse, with a laser based sensor.
PPS: There is a solution for this, it's waiting somewhere out there to be found ;)