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Looking for some advice/guidance

  1. Mar 18, 2012 #1
    Hi, I figured this would be a good place to post a question regarding testing apparatus. I want to test various computer mice for performance (specifically maximum speed) and I'm looking to build (or buy) something that would be able to spin a flat disc at variable speeds. For a similar purpose I've seen someone use an old belt driven record player but I'd prefer something that I could have a little more control over. Does anyone have any simple and preferably affordable solutions? Thanks.

    Edit* I should mention that I'm not an engineer or physicist.
     
  2. jcsd
  3. Mar 19, 2012 #2
    After reading my initial post over and thinking about the problem some more I think I can more clearly explain the problem domain. Basically what I need is a motorized lazy susan. I thought of trying to get a simple turn table but I'd rather have more control. While it wont be required to move anything of substantial weight it will still need to move whatever mousepad I use for testing and there is some friction where the mouse is in contact with the mousepad. Also I'd like it to rotate at a speed of 5 to 10 meters per second (I would need the ability to adjust the speed in some small increments).

    --Edit--
    After quite a bit of searching I think I've found a good solution. My only question is how would I go about calculating my power requirements? I'll be spinning a wooden lazy susan @ 5 meters per second (my calculations tell me that a 15in diameter lazy susan would need to rotate at 250rpm to get my desired speed) so I'm not sure if simple toy motor would work or if Id need something a little more powerful.
     
    Last edited: Mar 19, 2012
  4. Mar 20, 2012 #3
    If your looking to do this cheaply, you could use one of the small scooter motors with a belt drive or just driving your wheel directly and a regular scooter controller for it. That will give you from 0 to the max speed of the motor. Most of those 24/36 volt motors run a max speed of about 2500-3000 rpm. a 100 or 250 watt motor (standard outputs) should be plenty of power. Find a used one on craigslist or the local newspaper ads. 9 out 10 times the only thing that will be wrong with one is totally dead batteries where the charger died and was never replaced. I've used those little motors for all kinds of stuff.
     
  5. Mar 28, 2012 #4
    It doesn't matter what you're actually spinning, whether its a lazy susan or just a piece of wood you buy at a hardware store. Just get something circular and put it on an axle in the middle. Cheap particle board would be the best option. Put a cloth surface over it so the mouse has something to track.

    Why don't you just take a power drill that has a low-speed/high-torque mode, put a few hexagonal nuts on a screw to give the drill tip something to bite down on, and then connect the screw to a somewhat thin piece of wood/particle board. Put a sticker on the edge of the spinning piece, use a stopwatch to determine how long it takes for it to complete, say, 50 revolutions, and from that you can figure out its speed since you know its diameter.

    By adjusting how far from the axle/center of the spinning wooden circle you place the mouse, you can change the tracking speed of the mouse.

    You could test mice extremely quickly and accurately this way by starting reasonably close to the middle of the spinning disk and then moving towards the edge. Measure the radius at which the mouse starts producing errors, and using this value you can determine its max. tracking speed. The only issue here is that optical mice judge movement by rapidly imaging the surface below and calculating linear displacement between captured frames, and curvature, especially at the high speeds where they lose tracking, will be harmful to their performance. That is, the mouse might perform better on a treadmill spinning at 5 m/s than on a small circular disk whose surface directly under the mouse sensor is spinning at 5 m/s, since the movement of the treadmill surface is actually linear. Beyond a few inches from the axle, though, this will be negligible (which is why I'm suggesting you use the low-torque setting on the drill with a large circular surface rather than trying to spin a small disk very quickly).

    What you *don't* want to do is put something like the wheel from an R/C car on the edge of the round Susan, because the wheel speed will be variable depending on how much juice the batteries have left and on how hard you're pushing the wheel down to get traction (too much = friction losses, too little = slippage). With the drill system above, you'll get reasonably consistent spin rates assuming you're using a corded drill and not a battery-powered one.
     
    Last edited: Mar 28, 2012
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