[MPaulHolmes]

I added a mosfet to the controller. Now it can handle about 40 or 50 amps continuous I think. I'm going to hook it up to the car to test out the current limiting on a much larger motor (lower inductance and lower internal resistance, so harder to current limit). A whopping 6.7" diameter. Wow! hehe. They are 100v mosfets, so the 72v in the car shouldn't be a problem.

My 2 new oscilloscope probes came a couple days ago, so I can watch 2 mosfets at the same time (2 channels at once!). They need to turn on and off at almost exactly the same time, or else you get major problems. For example, at a 400 amp current limit, if 8 mosfets are supposed to be sharing the load, but one turns on faster than the others, then it's conducting all 400 amps for an instant! That's bad.

Fortunately, the 2 seemed to be perfectly in sync. I also put them in as far apart as possible, so they were a sort of worst case.

I experimented with etching 4 ounce copper with my baby drill press. It works really well, but it's sort of hard to do a straight line. It feels like sewing. First, you have the height of the drill just below the copper level. You push the PCB forward, following a line, stop the drill press, turn the PCB, turn on the drill press, push it again, following the line. It's fun!

I made a home-made hang glider a long time ago, and it brought me back to when I was sewing the cloth part.