I haven’t done a lot with the spinner lately. My last test was to make a straight horizontal line that was not along the axis. I had problems with that which I attributed to not having enough high resolution timers, so I set it aside to play with my electromagnet tests. But, one thing that was still bugging me was having to use alligator clips to turn the motor on and off. That didn’t make a consistently good connection and the motor speed was clearly unstable at time. So, I finally hooked up my 69¢ switch:

If you look close, you can also see the horizontal line test. In fact, now that I look at it, the right hand side actually looks like I expect. It’s a pretty straight line. The left side is also straight, just not horizontal. Hmmm… I wonder if my real problem is just with my algorithm for calculating the line. There may be some hope here yet…

But the switch works much better than my old technique. The motor reliably turns on and off and runs at a constant speed now! So future tests will go much more smoothly.