Paul & Sabrina's cheap DIY 144v motor controller

[flores]

Originally Posted by MPaulHolmes

I think I still have the "1000amp" code. I could look for it and try to make a change and email you the .hex file, flores.

Paul, did you find the code? Or can I use the one on the wiki with some changes? thanks.

[MPaulHolmes]

Hi Flores, I sent it so the motor amps should be around 1000. Try swapping TX and RX pins where it connects to the board (the cable). I may have swapped them on your board. Adam, I'm having trouble finding the code with the programmable motor amps. There's only like 40 possible projects, so I'm bound to run into it eventually. haha

[flores]

Thanks Paul, I've got them. Could you tell me which param you changed to up the amps?

I ordered a ttl serial usb adapter, so I can communicate directly with the atmega.. bypassing the max232.. that should work all the time.

Will flash the controller this weekend.. hoping for burning rubber.. not a melted busbar..

[MPaulHolmes]

I didn't change any parameter to up the amps. It was just changing the actual software.

[flores]

Okay.. then what did you change in the software? ;-)

It works by the way.. after flashing it has more power.. driven it several miles and it still works.

There were three 1000A beta units, right? Did all the others blow up?

[MPaulHolmes]

        // Now current is in the range [0,213] (if it's in 0 to 500amp for the LEM 300)
		// Now current is in the range [0,366] (if it's in 0 to 1000amp for the Melexis HB with 3/8" x 3/4" bus bar.  0.125" above bus bar.)
	current_fb = (loc_current_fb * 11) >> 3;			// (11/8 * 366 = 503)
	
	// current_fb = (loc_current_fb * 27) >> 4; //(27/8 is almost 506/298.  Use this for the 700amp version)
	// current_fb = (loc_current_fb * ??) >> ??; // ?? / ?? is almost 1000 / MELEXIS RANGE

	// now current is in [0, 510] or so, close to same as current reference range

I'm glad it's working! That one line up there that's not commented out is where the change was. The feedback from the current sensor is [512, 512+366], which gets translated to the interval [0, 366], which gets scaled to around [0,510]. Then, you can compare the throttle feedback, which is also in the range [0,510] to the current sensor feedback. That's because you are always trying to make the current sensor feedback match with the throttle position. To do the scaling from [0,366] to [0,510], I multiply by 11/8. It's not perfect, but dividing by 8 can be done with bit shifting. If I would have just multiplied by 510/366, I would have had to use actual division, and also LONG variables, which would have eaten up like 30 clock cycles or something like that. So, all the confusion comes from trying to make the code fast. It's many times faster to multiply by 11 (using 'short' multiplication), and then bit shift by 3 (which divides by 8).

I'm not sure what happened with the other 2 now. I know one of them had a bunch of funny issues, which I kept fixing, but could have been related to operator error and how it was hooked up. haha. It feels so long ago, I can't remember anymore.

[flores]

Thanks Paul.

I have a clamp amp meter that goes up to 1000A, but need a co-driver to check becuase all the high voltage wiring is in the back.. but will check it soon..

Is the 1000A out of beta if it works for me? The controlboard isn't that different from the 500A right? only the power stage is different.. but only the by the number of diodes and MOSFETS.. right?

You mentioned IGBT's.. should I convert it to that for testing? you mentioned plans with that... I'm willing to try anything for more poooooowwwwwweeeeerrrrrrrrrrr (quoting Jeremy Clarkson here)

[MPaulHolmes]

I've learned a lot in the last couple years. I cringe now when I see some details on the boards that I never noticed before. Mostly relating to loop areas. One problem with the board you have is the pwm signal from the control board is a VERY high impedance signal that's long and going through the air to the driver board. And I didn't even have the ground return wire close to it. It's like a big open circle of gaping noise collection. I added an extra ground wire to reduced the problem I think. Oh heck, I'm not even sure which one you have. haha.

The problem with the mosfet approach I used is there's such a small range of forgiveness for error. The mosfets are either 200v or 250v or something. With 600v igbts, it's idiot proof. And the layout I have worked out has a loop area that's very close to zero. And each of the 3 600v 600amp igbts has its own dedicated signal, and isolated supply. There's also the option to not even use hardware based pwm, and do it all in software, so I could allow for delays on the order of 0.00000005 second so as to make sure each igbt is turning on at essentially exactly the same time. There's always variation with the propagation delay from optocoupler to optocoupler, and I could eliminate that variation.

So to summarize, the new controller I want to do is a SBE ring capacitor, mounted upside down on top of three 600v 600amp igbts, all bolted to an aluminum plate. Each igbt driven by its own dedicated isolated supply/driver that can do 15amp peak. Each driver has a fault return signal that turns off everything if desaturation happens. The dimensions of the base plate would be around 12" x 15". Is that too big? I'm not sure how tall yet though. Maybe 4" or 4.5"?

-Paul

[jedsmd]

Paul
Are you planning to open source this design or is this going to be something you build and sell as a finished product?

There's also the option to not even use hardware based pwm, and do it all in software, so I could allow for delays on the order of 0.00000005 second so as to make sure each igbt is turning on at essentially exactly the same time. There's always variation with the propagation delay from optocoupler to optocoupler, and I could eliminate that variation.

If you are going to tweak the timing to account for variation in individual components is that going to require lab grade equipment and skills that will make it impossible for DIYers?

The dimensions of the base plate would be around 12" x 15". Is that too big? I'm not sure how tall yet though. Maybe 4" or 4.5"?

I can accommodate the 12x15 in my truck - it might be difficult for a person with a small car. But the power level is more than a small car needs anyway (imho --Flores may disagree).

Does anyone want to live dangerously and try out a prototype? I'd donate the igbts.

I would like to help if I can, I would be happy to pay for remaining components for a prototype and test it in the real world.
If you are going to open source, I could but one together and document it to start the assembly manual.
Jerald

[criley]

New guy here, with a few questions -

First, about me:
A few weeks back, I bought a dilapidated old golf cart to fix up. I use it to haul my son's sporting clays team around the course when they compete.

It all started off rather innocently, but quickly has turned into a nine headed hydra.

I found and fixed some broken connections, replaced battery wires, and got the cart running. It runs pretty well but slows down considerably going up hills. So I started looking for ways to make it perform better. My plan is to replace the controller with one that will handle more amps (current one is 200, my motor can handle 400), replace the mechanical forward reverse switch with a contactor, replace all the power carrying wires, possibly upgrade the motor and battery pack. I will probably end up driving it back and forth to work.

The controller in this thing is sealed. And there's no documentation on it! That drives me batty, because I'm one of those guys who has to know how things work. It's a failing. Also, I'm cheap. If something in the controller fails, I can't just replace the failed component, I'd have to replace the whole controller. Double whammy.

So I was thinking I might try building a controller and power board. I think I would like to build it with the notion that I might eventually upgrade to a 48 or 72v pack and up to 1000 amps. Initially I would limit to under 400.

I was looking at latest revisions of controller and power boards on the wiki.. but if something new is on the way which would require a guinea pig, I'm willing.

I have a lot of reading to catch up on, so bye for now!