Paul & Sabrina's cheap DIY 144v motor controller

[adamj12b]

apowers: You are right. When I really thought about it, I came up with the answer.

dwffy: Your welcome for the help. I have spent so much time with the controller and like to help when I can.

If you upgrade the firmware to the new stuff, you should not have any more throttle problems.

-Adam

[jackbauer]

Seems to be "Ask Paul a question week" so i'll have a go. Looking at a motorbike project and am intending to use 2 motors (48v 5kw) in series-parallel setup. Could the controller support this and could we add a contactor control for the shifting?

[adamj12b]

Originally Posted by jackbauer

Seems to be "Ask Paul a question week" so i'll have a go. Looking at a motorbike project and am intending to use 2 motors (48v 5kw) in series-parallel setup. Could the controller support this and could we add a contactor control for the shifting?

Of course it can!

I can set this up for you. Ive already made a reversing firmware and a motor temp shutdown feature with serial adjustability. You know how to get ahold of me.

-Adam

[MPaulHolmes]

Hi Jack! So, sometimes they are in series, and sometimes in parallel... What would happen if they are in series:
How does the wiring work? Battery pack + goes to Post1 of motor 1, then Post 2 of motor 1 goes to post 1 of motor 2, and then post 2 of Motor 2 goes to motor-? Each motor would see half of the pwmDuty*pack voltage? It would have greater inductance because there are more coils, so the PI loop might behave a little different. The change of current would be a little slower. But it might not be that big of a deal. I don't see a difficulty with series, but I've never tried it.

How about parallel?
Motor controller M- goes to post 2 of motor 1 and motor 2. Battery pack + goes to post 1 of motor1 and motor 2, right? Now, the pwmDuty*pack voltage would be the same for both, but the current would have to be twice what it normally would be with a single motor to get the same torque for each one. I don't see why the controller would have a problem running 2 at the same time. Would the equivalent inductance be half? I think so. So, the current could change fast, so you might have to program your PI loop to be slower changing to account for this case. Or, you could change the PI values on the fly depending on if the motors are in series or parallel.

Now, how about switching between the 2... It seems like some subtleties could creep in if you aren't careful. If there is a moment when neither motor is connected when switching between parallel and series, you could have dwffy's problem if the throttle was nonzero.

[adamj12b]

I would set it up with micro switch's ont he contactors to check the position of the contactors. If they changed then apply throttle, else throw an error or go back to normal operation.

-Adam

[MPaulHolmes]

So, you would want to start in series mode, which has greater torque, and then switch to parallel mode for higher top speed. The goal is to maximize torque I guess, which is to say, maximize current. How could you do that automatically without a speed sensor? That would be nice!

[jackbauer]

Originally Posted by MPaulHolmes

So, you would want to start in series mode, which has greater torque, and then switch to parallel mode for higher top speed. The goal is to maximize torque I guess, which is to say, maximize current. How could you do that automatically without a speed sensor? That would be nice!

Yeh thats its exactly. Say the controller pushes 200amps through the motors in series mode. Then each motor gets 200amps at half the voltage to maximise starting torque. Then when sufficient speed is obtained , switch to parallel. Now each motor would see 100amps but full pack voltage for max speed. Sort of like a 2 speed gearbox. My plan is to have a thumb switch for the driver (rider?) to change up or down. This is a drawing done by Tesseract over on diy.

[Dwffy]

Hi Paul,
I've been working on my potentiometer and rebuilt it so that it now has a range over the full %k of the pot. It can read from 3.4 ohms to 5.1k ohms. Using gears was the only way I could think of to get the full range of the pot using the travel limited by the accelerator cable. When the micro switch turns on it reads 50 ohms. I've included a pic of it for you to see too. There will of course be a cover over the whole contraption to eliminate dust etc.
I would like to know what is the best way to connect the pot and microswitch according to you. You've seen how I connected mine up and perhaps I should not be connecting it up this way.

[MPaulHolmes]

Hey Dwffy! Man, you are mechanical. That's beautiful! It would have taken me a year to come up with something like that. I tried too, and gave up. You should check out my car build thread sometime. It has my homemade pot. It was horrible.

Well, All that really matters is that the microswitch comes on some time before about 500 Ohms. 50 Ohms is very safe I think. OH! I forgot. My friend wrote an email to me about this very issue. He designed the control board in the first place, and is an actual professional electrical engineer. You might want to consider his idea. I'll forward it to you.

[Greg Fordyce]

Originally Posted by MPaulHolmes

Well, All that really matters is that the microswitch comes on some time before about 500 Ohms. 50 Ohms is very safe I think. OH! I forgot. My friend wrote an email to me about this very issue. He designed the control board in the first place, and is an actual professional electrical engineer. You might want to consider his idea. I'll forward it to you.

I am getting close to getting my car on the road with the Cougar controller. When I had a Curtis I had wired a contactor to the microswitch as dwffy had done, but I don't think I will be doing that now. Paul I am interested in this idea as well, could you enlighten me? Thanks,

Greg