Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

Hi Matt! I tried to email you the whole file, but it was limited to 5000 characters, and the program was 13000.

I think I misspoke earlier. (actually I didn't know how to describe what it does. hehe. but here it is!)

Let's say current % of max current is less than or equal to the throttle position. Then PWM duty just follows whatever the throttle is.

Now let's say current % is larger than throttle position. Then PWM duty keeps falling until current is less than or equal to throttle position. Now PWM duty just goes back to following throttle position, until current gets bigger than throttle position.

[MPaulHolmes]

Sorry Matt, it wouldn't let me send the whole thing by PM.

Basically, here's the important part:

if (pwmDuty > throttlePos) {
pwmDuty = throttlePos;
}

else if (current > throttlePos) { // The poor man's PI loop! hahaha!
if (pwmDuty)
pwmDuty--;
}

else if (pwmDuty < throttlePos) {
pwmDuty++;
}


OCR1A = pwmDuty;

[esoneson]

Paul,

There may be another variable that you will want to incorporate into this algorithm. You will probably want to be able to limit the rate of change of speed (or pwmDuty or Current). I.e. limit accelleration. Or have an acceleration curve (when speed is very slow keep acceleration low, when higher allow higher rates of acceleration to keep from jerking the car right from the git-go. Also if in reverse, then acceleration should also be tamed.

For the future: selectable acceleration curves from granny to grandprix

EDIT: Also, for deceleration you might want to be more aggressive about the adjustment. If you see the cop in your rear view mirror and take your foot off the accelerator, you want instant response, no?

Eric

[MPaulHolmes]

Oh man, you are right Eric! I forgot about that. I had it in there before on the bike version, and messed around, then changed a bunch of stuff and forgot about it. That's a really good idea. I think I'll test it out ON THE ROAD HAHAHAHA with different acceleration ramps and see how it feels. I like the idea of granny mode to drag race.

Thanks, Eric!

[lectruck]

This is great. Granny mode to drag race, you all are doing great.

What does it take to adopt a poor little moffet, this is such a worth while project I can't bear to think that they haven't all been taken care of yet.

[MPaulHolmes]

Actually there are a few mosfets that are still homeless. hehe. You can make a donation here:

Green Cars: Videos and More!

On the right side it says "Support the 144v Open Source Motor Controller!"

It's Ben's site. He graciously set that up for me! Thanks Ben!

[tinkerdave]

Read this all in one sitting. This is great. Eyes are bleeding.
Thanks for the chance to be involved and adopt a FET.
When I was coming up all we had were glass FETs.

So, can you all point me in the direction of motor specs.- vs- vehicle weight and other beginner stuff?

Thanks Paul for the hard work!

[MPaulHolmes]

Hi Dave! A great place for every question you could ever come up with about building your own EV is EVDL Archive / Forum Interface - Electric Vehicle Discussion List.

What I would do when Sabrina and I made our conversion is write questions on there each day, and like 10 or 20 world experts with 40 years of EV experience would give their advice! hehe. and it's free!

[esoneson]

Another very userfull site is:
DIY Electric Car Forums - Electric Vehicle Build and Conversion Community

There are some very knowledgeable people there including some folks building a really beefy DC Controller (but out of my economic sphere).

Eric

[MPaulHolmes]

Here it is where the curtis used to be.

I took it for a short drive around the neighborhood, not going too fast, and accelerating gently. It was sort of stressful and scary, not knowing if something was going to catch on fire or something. I still have a headache from it. I

I need to fine tune the delay after the hardware shuts off the mosfets. I had put in a really long one earlier and forgot to change it back to something more reasonable, and when I was at a standstill on the driveway, trying to go up, I hit the current limit and the delay was so long (like 1 millisecond or something) that the current dropped all the way to like 0 by the time it turned on again, causing the average current to be very small on very steep hills at near 0 rpm.

So, I need to reduce the delay so that the current doesn't fall that much below the 500 amp limit before being turned on again. People may actually need all 500 amps at start up (going up a really steep hill!) Geeze!

Now is the super annoying part. I don't have a laptop, so I get to unbolt everything, and drag that dang thing into our bedroom to re-program it with a shorter delay, and then re-bolt in everything! Dang it! I need to get a nice cheap laptop.

I'm too stressed to feel happy right now. It was scary having it in the car, and imagining all the fire explosion scenarios! I'm glad it works, though!