6 ms·

Show HN: I built a custom USB Trackball

126 points by xythobuz 4y ago

ocimbote 4y ago
Overall, I'm impressed. Very much. Now, I'd love to see a picture of how a hand is supposed to sit above or around this trackball because I can't picture how fingers can comfortably reach the 4 buttons just by looking at their location on the device. Which leads me to the personal opinion: I think I prefer the design of the testbed over the final iteration. Buttons are missing, I know, but... Here I stand nonetheless.
floren 4y ago
Well done, shame about the ergo problems! Hopefully with some iteration, it could be more comfortable. My recommendation: don't be afraid to take up more desk space :) I'd try something which put the button caps in an upward-facing orientation instead of facing out. When I built my mouse (https://jfloren.net/bellwether.html https://jfloren.net/bellwether.html) I found that in the past there were these neat modules which packaged a sensor and a microcontroller on 1 chip, and you basically just had to wire it up to USB -- but those don't seem to exist any more! So I picked essentially the same Pixart sensor as you, used the same leaked datasheets, and built my own. I do wonder why the all-in-one devices disappeared, though.
- fragmede 4y ago
  Is a micro with a PLC (or just a fast enough adc+CPU these days) connected to a photodiode fast enough to do it in software? Actually it seems modern devices use a CCD and then process the image.
  - convolvatron 4y ago
    i think you'd have a hard time determining the direction from just one sample
    - fragmede 4y ago
      for the photodiode you'd use to perpendicular sensors
- xythobuz 4y ago
  Awesome project! Yes, I've also thought about mounting the switches vertically. And more surface should also provide more grip on the table.
freitzkriesler2 4y ago
.de Why am I not surprised? I love Germany .
metadat 4y ago
Server is currently hugged to death and timing out for me. In the meantime, enjoy the sweet nectar of an archive.org snapshot link (collected yesterday): https://web.archive.org/web/20230217104641/https://www.xythobuz.de/trackball_v1.html https://web.archive.org/web/20230217104641/https://www.xytho...
mkl 4y ago
I would like to make custom trackballs, and pool balls are a great idea. I would want a scroll ring like my Kensington Expert mice (https://duckduckgo.com/?q=kensington+expert+mouse&t=fpas&iax=images&ia=images https://duckduckgo.com/?q=kensington+expert+mouse&t=fpas&iax...). Any idea how to make such a thing?
- duskwuff 4y ago
  Optical quadrature encoder, much like how mechanical mice worked. Make the ring with a series of evenly spaced holes on the inside, then use a pair of optical sensors across that track of holes to detect when it's moving and in what direction.
  - mkl 4y ago
    Looks like you're right: https://softsolder.com/2013/03/18/kensington-expert-mouse-trackball-scroll-ring-aperture-alignment/ https://softsolder.com/2013/03/18/kensington-expert-mouse-tr.... Using another mouse movement sensor and ignoring one dimension might be simpler for DIY. I don't understand how to get the stepped motion of the Kensington scroll rings and most mouse wheels. Maybe it has bumps to move past.
    - duskwuff 4y ago
      Hah, I'd never looked inside one before but that's exactly how I'd imagined it would work. The optics for a quadrature encoder are very forgiving -- it's much easier to implement than the camera-based sensor that's used for position, which requires a plastic lens. > I don't understand how to get the stepped motion of the Kensington scroll rings and most mouse wheels. Maybe it has bumps to move past. Most mouse wheels use a mechanical rotary encoder, and the detents are inherent to that part. Some of the fancier ones use custom mechanisms.
      - cfraenkel 4y ago
        The Expert Mouse scroll ring originally was designed with a neodynium magnet and a steel slotted ring to provide the detents. The two I currently have don't have a scroll ring detent, so presumably the magnet was removed as a cost saving and/or reliability change. (for standard mouse scroll wheels, you buy the encoder with the detents already built in.)
gyf304 4y ago
Something about the use billiard balls immensely amuses me. I'm impressed.
cfraenkel 4y ago
FYI - if you make another iteration (or build it into your keyboard), strongly recommend moving the sensor away from directly below the ball. For reasonable ergonomics - you want the top of the ball as close to the desk surface as possible. The 5 ~ 10 mm you need to fit the sensor package makes a big difference. When prototyping the Expert Mouse, we found that offset angles as high as 20 degrees weren't really noticeable, and that allowed the ball to sit just barely clearing the bottom plastic case. (That and use the smaller 51 mm billiard ball instead of the American 2.25" ball)
- mbreese 4y ago
  Looks like they used an even smaller ball. I didn't know 38mm pool balls were a thing... > To be able to call this a trackball, we also need some kind of ball or sphere of course. Many people go with the smallest regulation billard balls with a diameter of 38mm.
- xythobuz 4y ago
  Interesting, I did not think about the possibility of moving the sensor to another position. But it makes sense. The Logitech Trackballs I've seen also have a slight offset that could be in the ballpark of 20 degrees. I will have to do some further experimentation. Thanks!

126 points by xythobuz 4y ago

Overall, I'm impressed. Very much. Now, I'd love to see a picture of how a hand is supposed to sit above or around this trackball because I can't picture how fingers can comfortably reach the 4 buttons just by looking at their location on the device. Which leads me to the personal opinion: I think I prefer the design of the testbed over the final iteration. Buttons are missing, I know, but... Here I stand nonetheless.

floren 4y ago

Well done, shame about the ergo problems! Hopefully with some iteration, it could be more comfortable. My recommendation: don't be afraid to take up more desk space :) I'd try something which put the button caps in an upward-facing orientation instead of facing out. When I built my mouse (https://jfloren.net/bellwether.html https://jfloren.net/bellwether.html) I found that in the past there were these neat modules which packaged a sensor and a microcontroller on 1 chip, and you basically just had to wire it up to USB -- but those don't seem to exist any more! So I picked essentially the same Pixart sensor as you, used the same leaked datasheets, and built my own. I do wonder why the all-in-one devices disappeared, though.

fragmede 4y ago
Is a micro with a PLC (or just a fast enough adc+CPU these days) connected to a photodiode fast enough to do it in software? Actually it seems modern devices use a CCD and then process the image.
- convolvatron 4y ago
  i think you'd have a hard time determining the direction from just one sample
  - fragmede 4y ago
    for the photodiode you'd use to perpendicular sensors
xythobuz 4y ago
Awesome project! Yes, I've also thought about mounting the switches vertically. And more surface should also provide more grip on the table.

freitzkriesler2 4y ago

.de Why am I not surprised? I love Germany .

metadat 4y ago

Server is currently hugged to death and timing out for me. In the meantime, enjoy the sweet nectar of an archive.org snapshot link (collected yesterday): https://web.archive.org/web/20230217104641/https://www.xythobuz.de/trackball_v1.html https://web.archive.org/web/20230217104641/https://www.xytho...

mkl 4y ago

I would like to make custom trackballs, and pool balls are a great idea. I would want a scroll ring like my Kensington Expert mice (https://duckduckgo.com/?q=kensington+expert+mouse&t=fpas&iax=images&ia=images https://duckduckgo.com/?q=kensington+expert+mouse&t=fpas&iax...). Any idea how to make such a thing?

duskwuff 4y ago
Optical quadrature encoder, much like how mechanical mice worked. Make the ring with a series of evenly spaced holes on the inside, then use a pair of optical sensors across that track of holes to detect when it's moving and in what direction.
- mkl 4y ago
  Looks like you're right: https://softsolder.com/2013/03/18/kensington-expert-mouse-trackball-scroll-ring-aperture-alignment/ https://softsolder.com/2013/03/18/kensington-expert-mouse-tr.... Using another mouse movement sensor and ignoring one dimension might be simpler for DIY. I don't understand how to get the stepped motion of the Kensington scroll rings and most mouse wheels. Maybe it has bumps to move past.
  - duskwuff 4y ago
    Hah, I'd never looked inside one before but that's exactly how I'd imagined it would work. The optics for a quadrature encoder are very forgiving -- it's much easier to implement than the camera-based sensor that's used for position, which requires a plastic lens. > I don't understand how to get the stepped motion of the Kensington scroll rings and most mouse wheels. Maybe it has bumps to move past. Most mouse wheels use a mechanical rotary encoder, and the detents are inherent to that part. Some of the fancier ones use custom mechanisms.
    - cfraenkel 4y ago
      The Expert Mouse scroll ring originally was designed with a neodynium magnet and a steel slotted ring to provide the detents. The two I currently have don't have a scroll ring detent, so presumably the magnet was removed as a cost saving and/or reliability change. (for standard mouse scroll wheels, you buy the encoder with the detents already built in.)

gyf304 4y ago

Something about the use billiard balls immensely amuses me. I'm impressed.

cfraenkel 4y ago

FYI - if you make another iteration (or build it into your keyboard), strongly recommend moving the sensor away from directly below the ball. For reasonable ergonomics - you want the top of the ball as close to the desk surface as possible. The 5 ~ 10 mm you need to fit the sensor package makes a big difference. When prototyping the Expert Mouse, we found that offset angles as high as 20 degrees weren't really noticeable, and that allowed the ball to sit just barely clearing the bottom plastic case. (That and use the smaller 51 mm billiard ball instead of the American 2.25" ball)

mbreese 4y ago
Looks like they used an even smaller ball. I didn't know 38mm pool balls were a thing... > To be able to call this a trackball, we also need some kind of ball or sphere of course. Many people go with the smallest regulation billard balls with a diameter of 38mm.
xythobuz 4y ago
Interesting, I did not think about the possibility of moving the sensor to another position. But it makes sense. The Logitech Trackballs I've seen also have a slight offset that could be in the ballpark of 20 degrees. I will have to do some further experimentation. Thanks!