Paul & Sabrina's cheap DIY 144v motor controller

[mcudogs]

Hey Paul,

Sorry that's my fault, I printed the pdf without reversing the layout. It is printed so you can overlay the top over the bottom and the holes will line up. It's easier to check it that way. To etch the board I would have printed it in reverse.

Have you thought about using connectors between the 2 boards instead of wiring? It would make the whole assembly a bit easier. It looks like you are using tapped spacers to hold the boards together, so connectors could be the way to go.

mcudogs

[jyanof]

Originally Posted by esoneson

Congratulations jyanof, so far that is good news!

I think we all know that Paul has a VW with 72 volt system. For my feeble self, I can't remember if you spelled out your specs. What are the basics of your EV? Model, drive train, weight? That will help in the comparisons.

Thanks,

Eric

Eric, Paul and All,

I started a new thread with details of the testing. I'll probably still post updates here, but I think it'll be easier if most of the details/questions/results pertaining to this controller testing are located together in a cohesive thread.

http://ecomodder.com/forum/showthrea...ting-9325.html

[MPaulHolmes]

So, I tried a new throttle idea that Joe had (you know! The guy doing the DIY EV charger!?). It's really a very good idea. It works really really well, too. OK, you basically make throttle proportional to pwmDuty*current, rather than to current or pwm duty! Now, pwmDuty is proportional to the voltage, so basically, this make the throttle proportional to POWER!!! If you want full power, push the pedal down the whole way. If you want only a little power, then only push the pedal down a little. It feels really really good. I tried it out today with Ben's controller. I just did some ramping code so the power chases the throttle rather slowly. I'll also try a PI loop so that the power will chase the throttle like you know who chases a pound of bacon, then I'll have settings for how fast the throttle response is, on a scale of like 1 to about 16, where 16 is the most responsive.

It's one of those ideas that is so simple and so pretty, that you just have to say, WHY DIDN'T I THINK OF THAT!!!!!!!!!!!!!!!!!!!!! MAKES ME MAD!!!!! HAHAHA!

[jyanof]

oh yeah, i'm excited for this!

[mcudogs]

Paul, Latest mods to the power board are attached. I have added the 2 Gnd connection vias, couldn't get them to line up perfectly with the control board but they're close. I also moved the u shaped etches up for the B+.

I have included the solder mask layers for the top and bottom of the board. The solid areas will be tinned with solder. I am not sure whether the M- bus bar was mounted on the top or bottom of the board so I have both sides tinned for M-.

Can you tell me where I can get a copy of the control board PCB file (not gerber) .pcb or equivalent?

[rollins]

I'm new here, and I've only been studying electronics for just over 1 year. So forgive me if I am out of context.

I've been studying the schematic Rev2C and have a couple of suggestions.
1) I think D9 should be a 5 volt Zener.
2) I think you should use a Schmitt Trigger on the comparators U8A and U8B. Schmitt trigger - Wikipedia, the free encyclopedia

[chapper]

mcudogs: Nice work, PCB looks good.

I'd suggest an alteration that seems right, but I'm not sure it's necessary.
On the 1B top layer, the negs of the capacitors are on isolated islands. I'd connect them with a horizontal band at the top edge, about 0.50" so that you have a 5-fingered comb (B-) pointing down, and a 4-fingered comb (B+) pointing up.
Adjust the bottom layer so that you have a 4-fingered comb (B+) pointing down, and a 5-fingered comb (B-) pointing up. You also have the opportunity for 4 more B- vias.

It came to me while considering current balancing-equalizing, and all those opportunities to short B+ and B-.

It seems there should also be a fabrication drawing, with dimensions, hole sizes and conditions, notes, etc.

A question I would pose: Is current flow affected by sharp corners on a PCB trace? I know corners can be an issue with high frequencies. How about high current?

John

[blackpanther-st]

Originally Posted by MPaulHolmes

So, I tried a new throttle idea that Joe had (you know! The guy doing the DIY EV charger!?). It's really a very good idea. It works really really well, too. OK, you basically make throttle proportional to pwmDuty*current, rather than to current or pwm duty! Now, pwmDuty is proportional to the voltage, so basically, this make the throttle proportional to POWER!!! If you want full power, push the pedal down the whole way. If you want only a little power, then only push the pedal down a little. It feels really really good. I tried it out today with Ben's controller. I just did some ramping code so the power chases the throttle rather slowly. I'll also try a PI loop so that the power will chase the throttle like you know who chases a pound of bacon, then I'll have settings for how fast the throttle response is, on a scale of like 1 to about 16, where 16 is the most responsive.

It's one of those ideas that is so simple and so pretty, that you just have to say, WHY DIDN'T I THINK OF THAT!!!!!!!!!!!!!!!!!!!!! MAKES ME MAD!!!!! HAHAHA!

Paul this sounds like it would work really well; enough so that I am re thinking about not using straight PWM for the controller I am working on. I probably will skip the PI loop, but the direct throttle = power formula is just exactly the response I want.

Don't get me wrong though, I am not saying that the PI loop is a waste or bad idea, it's just like I mentioned before we are building different controllers for different intentions. Personally I want that anamalistic aggressiveness, that when I put my foot down I have power that very instant, and the same for letting off. but as you mentioned that can result in a rough and jumpy ride for many drivers who would be better off with a more domesticated code approach.

[MPaulHolmes]

I messed with the throttle proportional to power in a variety of contexts, and it works perfectly in some, and acts really weird in others. I'm starting to think that there are different stages where different throttles are appropriate, and maybe a speed sensor is needed to help decide when to switch throttle types. Maybe throttle proportional to torque near 0 rpm, throttle proportional to power once the motor is spinning, throttle proportional to speed at some time???

Say you are on a very steep hill. Let's pretend the Duty is 1 (scale of 0 to 512), and the current is 512. Well, that can happen if the throttle is 1.

Here's some pseudo-code:

power = pwmDuty*current/512.
adjust pwmDuty until power = throttle.

It does NOT feel good to have the current go to 500 when the throttle is almost 0. At least the hardware overcurrent circuit saved my bacon.

Throttle proportional to power feels AWESOME when you are moving. It does NOT feel awesome when taking off. We need a dang speed sensor. There, I said it! hahaha!

Without a speed sensor, the best feeling throttle that I have felt is the current PI loop. Another good one is the one that sort of integrates the speed with torque (ramping code).

[dlaing]

Paul,
What do you think of the back emf that dcb suggested? I put a couple links to it in post #2045. It sounds like it's most important when the throttle is minimal turning off the pwm to check the current and voltage should be less noticeable.