View Single Post
Old 04-09-2009, 12:59 AM   #817 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
Posts: 3,832

Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
Thanks: 1,368
Thanked 1,202 Times in 765 Posts
Originally Posted by bennelson View Post
Hey Paul,

I believe the controller is making a bit of a squeal/whine at times.

If you watch the tire spinning video, a split-second before the wheels start to spin, you can hear it.

Did you notice that at all when you were testing it? Is it part of the PI looping thing? It seems to happen when accelerating.

This video is also one of the few times I have HEARD the Metro in action. Inside the car, it's kind of loud, because most of the interior is removed. On the outside, all you hear is traffic, the wind, and flying gravel!
It is the hardware over-current shutdown coming on, and going off again super fast, oscillating around 480 amps(???) or so. I have some ideas about how to fix that. When I had a long delay after each over-current shutdown, it would make a lower frequency buzz. Now that I got rid of the delay, it's turning off for a shorter period of time, and then turns the mosfets back on.

One thing that should help is using the 300 amp current sensor, which still has a range of 900 amps. It will give me almost double the resolution of the 500 amp current sensor. Instead of 0 - 500 amps corresponding to 0v to 0.6v current sensor output, it will be 0-500 amps <--> 0v to 1v. Not great, but better. I'm also going to try some things that will reduce the noise, like sampling at the same point on the PWM wave each cycle.

MODELING: I have never done any of that! That sounds like a great idea for really making clear directions. The problem is, I need a fixed predictable supply of power section PCB (4 or 5 ounce copper would be really nice!). Right now, the directions would be bent toward using the supplies and dimensions of PCB that I have available, rather than toward optimal functional design. I have enough 3 ounce 2 sided PCB for maybe 40 or 45 controllers. It's not perfect, but the price was right ($1 each!).

By the next version, I'll try to be really careful about the dimensions. I was sort of just winging it on this one, since I have to finish it before May 2nd, so I can go to the Lacey Alternative Energy Fair. I'm almost done, though! I've been using ExpressSCH, which is a circuit modeling software. I could convert that to a .jpeg which could then be turned into something nicer with professional modeling software.

It's getting much much easier to make one from start to finish. After a bit more practice, I bet I could do one in like 1 or 2 days!
kits and boards
  Reply With Quote