big ball

I don’t think that the Orbit is this large, but about twenty years back, IIRC, Kensington had some trackball that had a ball that could be removed and had the same dimensions as standard-sized pool balls, so if you wanted to use pool balls, you could. There are all sorts of crazy pool ball designs out there.

kagis

Yeah, sounds like the Orbit uses a 40mm diameter ball. A standard American pool ball is apparently 2.25 inches (57.15 mm).

Sounds like the device in question was the: “the old mechanical Kensington Turbo Mouse Pro and Expert Mouse Pro”. This guy says that he had some trouble trying to use the balls on newer trackballs with optical sensors, as they don’t detect the ball well-enough:

https://www.trackballmouse.org/kensington-expert-wireless-8-ball-and-9-ball-trackball-prototypes/

But of course, I had to try and put the ball in my (more than 10 year) old and trusted USB Wired Expert as well. The ball fits perfectly (it’s the same size)… but the optical tracking didn’t really work, especially on the white / yellow 9-Ball, and the white parts of the 8-Ball. It results in stop and go movement of the mouse cursor.

Hmm.

The “stop and go” thing sounds familiar. One thing I suppose someone might do is to electrically-modify the trackball. I once had a trackball with a translucent pink ball that I used in a dark room. It had a red LED. This meant that the trackball would visibly glow, which was obnoxious. It also had USB power-saving, so the LED would go to a low-power state after a few seconds of non-movement, go to high-power state when you started moving the ball, which meant that it would visibly change brightness. I liked using the thing from a mechanical standpoint, but the glowing, flashing pink ball was very distracting.

CCD sensors can not just detect visible light, but also infrared, unless they have a filter on them to try to exclude it. Infrared light wouldn’t be distracting to my eyes, and if it was enough for the trackball sensor, that’d be great. I figured that it was worth a shot, see i I went out to mod the thing. Bought an infrared LED, got some solder wick, disassembled the trackball, desoldered the red LED, swapped in the infrared LED and powered the thing up. And it worked! No (visible) glowing or flashing. Sort of. Problem was that it worked fine when I was moving the ball, but when I had my hand off the thing for a while and started moving it, it didn’t reliably pick up on movement. My guess was that the sensor had a harder time picking up the ball surface when illuminated by infrared than the visible red light, and so when the trackball went into USB power-saving mode, had a dimmer light, and it was pretty marginal to be able to detect movement.

In my case, I went and dug up the datasheet for the chip used in the trackball, hoping that there was some nice, external input that’d let me disable power-saving — the trackball was attached to a desktop, so I was fine leaving it in high-power mode all the time. Sure enough, one pin on the chip indicated whether it was in low power mode or not. Soldered a wire to that pin and bam, thing worked fine even when just starting to roll the trackball.

But if they’re getting stop-and-go detection, might be the same sort of thing, that the pool ball isn’t as reflective or is more reflective. Like, it might be worth slapping a pool ball in and also getting a higher-luminosity (or lower-luminosity, if the issue is the image being blown out) LED. Might also try adding features to make it easier for the camera to see moving details — I guess that drawing on a pool ball would ruin the aesthetic, but maybe it’d be possible to use a permanent infrared marker.