Mouse Destruction Part Two

Mouse Destruction

So, now that I've got the basic exploded mouse working, the next step is to make it useful.

Basically, I want to have a wheel of some sort that acts as a precision odometer. For this, I need a rotating shaft that holds the mouse encoder wheel, and some sort of enclosure that holds the sensor in alignment. Also, I'd like the whole thing to be essentially dustproof.

My first attempt was educational, but ultimately a failure. I was hoping that the solid 24gague wires I wired the thing together with would be solid enough to hold the sensor in position. Unfortunately, it just wasn't stable enough.

To hold my encoding wheel, I am using a shaft that I scrounged off of something (probably a floppy drive or CD-ROM). I've got a dozen or so of these.

I cut the encoder wheel with a hobby saw, so that it was just the wheel with a hole in the middle (if your mouse is different, you may also need to drill a hole). I put some electrical tape around the shaft to make it thicker, and friction fit the encoding wheel onto it. This part seems to have worked out very well.

Earlier, I had bought a bunch of tiny tupperware containers from the dollar store - something like 9 or 12 for a dollar. They're a perfect size to hold everything, and have the bonus of being dustproof.

For my first attempt at mounting the shaft in the container, I just drilled some holes through the side of the container to hold the shaft. I started out with small holes, and gradually grew them until they were big enough. On one side, I did a final ream of the hole with the drill at an angle, so I could get the shaft in.

This part worked ok-ish. The shaft rotates well against the tupperware plastic. The main issue I have here is with side-to-side movement. I don't own any shaft collars, so I tried electrical tape and plastic. It worked poorly, and I had too much side-to-side play. I need a better solution for holding the shaft in place. Maybe I'll just break down and buy something. :-(

Next, I needed to put the sensor in place. I cut a rectangular hole in the side of the container for the ethernet jack with a utility knife. To ensure a tight fit, I started with a small hole, and gradually enlarged it until the jack just snapped in place.

This part worked well. The ethernet jack holds tight.

Finally, I tried to line up the sensor, by simply bending the wires and putting it in place. In the end, this worked very poorly. I was able to get it to operate, but not consistently. I tried putting some plumber's putty in the container to help hold things in place, but it didn't help.

In the end, the problem seems to be twofold: the shaft has to have less side-to-side play, and the sensor needs to be fixed in place relative to the wheel. Otherwise, if the ethernet jack is stressed, or the container is moved, you lose precision. The fact that the container can flex makes things worse.

I think you could use this design as-is, but it would always be finicky and unreliable. The whole point of this thing is to have a reliable position sensor so I can use cheaper motors and simpler controls. So it's back to the drawing board.

I think my next attempt might involve some rigid plastic from a cutting board, to help build more of a structure to attach things to.