Paul & Sabrina's cheap DIY 144v motor controller - Page 326 - Fuel Economy, Hypermiling, EcoModding News and Forum

MPaulHolmes · 03-23-2010, 03:00 AM

I finally got the GCode written for the 1000amp controller, and etched both sides of a prototype. I am also mostly done with drilling the holes in the PCB, and the heat spreader is all nice and milled super flat and shiny. I sanded it down with 1500 grit sand paper. I'm debating maybe only putting on like 5 - 7 mosfets and 5-7 freewheel mosfets just for the prototype, so it would only be a 500-700amp controller, just for testing purposes. I don't have a motor/coupler/anything that can really test 1000 amps safely. I mostly want to make sure everything turns off and on when it should. There's not a lot of room for error with synchronous rectification.

ludiagsm · 03-23-2010, 04:02 AM

Quote:

Originally Posted by MPaulHolmes

I finally got the GCode written for the 1000amp controller, and etched both sides of a prototype. I am also mostly done with drilling the holes in the PCB, and the heat spreader is all nice and milled super flat and shiny. I sanded it down with 1500 grit sand paper. I'm debating maybe only putting on like 5 - 7 mosfets and 5-7 freewheel mosfets just for the prototype, so it would only be a 500-700amp controller, just for testing purposes. I don't have a motor/coupler/anything that can really test 1000 amps safely. I mostly want to make sure everything turns off and on when it should. There's not a lot of room for error with synchronous rectification.

good news

KISA · 03-23-2010, 07:11 AM

Sorry for this questions if it's already been asked, I've looked through a fair number of this forums pages (not all 327 of them) and couldn't see it. But Murphy's law will say it was probably on the next page

I'm just wondering what is the need for so many capacitors. I understand they add when in parallel so it affectively 16 x 820uF, roughly a 200V 17mF Capacitor. Is the high capacitance needed to successfully smooth out the voltage swing caused by the mosfet switching frequency or am I completely off the path?

The reason I ask it that I'm trying to determine what capacitance I will require for a controller I wish to build/test for an electric motorbike and what are the contributing factors?

Thanks,

Markus

ga2500ev · 03-23-2010, 08:27 AM

Quote:

Originally Posted by KISA

Sorry for this questions if it's already been asked, I've looked through a fair number of this forums pages (not all 327 of them) and couldn't see it. But Murphy's law will say it was probably on the next page

Probably considering this question was just asked last week. See page 325.

Quote:

I'm just wondering what is the need for so many capacitors. I understand they add when in parallel so it affectively 16 x 820uF, roughly a 200V 17mF Capacitor. Is the high capacitance needed to successfully smooth out the voltage swing caused by the mosfet switching frequency or am I completely off the path?

It's not just the capacitance. There is also the issue of effective series resistance (ESR) and heat dissipation, because the ESR causes the caps to heat up.

The best explanation that I've read so far is Lee Hart's discussion on motor controller capacitance. You can find it here:

Yahoo! Groups

Talks about ESR, ripple current, heat, the whole nine yards. The short of it is that more is more is better to a point, and that the specs of the caps in terms of ESR and temperature are very important. Finally he has an empirical way of determining the correct amount, which measures the ripple current to determine the appropriate amount.

Quote:

The reason I ask it that I'm trying to determine what capacitance I will require for a controller I wish to build/test for an electric motorbike and what are the contributing factors?

See above. Everything you need is there.

Quote:

Thanks,

Markus

Welcome.

ga2500ev

KISA · 03-23-2010, 09:28 AM

Awesome, thank you very much for the quick reply and help ga2500ev. It's very much appreciated.

I actually started from the beginning of the forum and went for a while, then thought maybe I'd have more luck starting from the end, but after looking at 327 and 326 though it was futile and stopped, how bizzare is that? Bloody Murphy

MPaulHolmes · 03-24-2010, 03:32 AM

hahaha.

OK, I finished the SR control board. It will work this time, or my name is aunt Hilda! I just submitted it to PCB International, which offered to try to convert the PCB Artist file!!! The president wrote to me! He read about our projects on ecomodder, and offered to help! It's really a good price too, for 4 boards, it's like $95 or something. I forgot. He wasn't sure if they would be able to convert the file format, but I really really really hope so! I can afford $95! Oh please work! Also, I finished the stupid etching of the pcb, and finished drilling the dang heat spreader, having to dig out 2 stinking broken drill bits. makes me mad. Then I cooked my fingers since I tried to grab the drill bit, which was approximately 40000 degrees. My skin started to smoke immediately! It smelled super good! But then it hurt really bad.

Hey! we are leaving in the morning to go to Phoenix for almost a week! hurray to see Sabrina's friend.

bye!

bigh · 03-24-2010, 09:08 AM

Quote:

Originally Posted by MPaulHolmes

hahaha.
OK, I finished the SR control board. It will work this time, or my name is aunt Hilda! I just submitted it to PCB International, which offered to try to convert the PCB Artist file!!!

Congratulations! thats great news. I'm very much looking forward to the CAN Bus based boards.

Quote:

Originally Posted by MPaulHolmes

My skin started to smoke immediately! It smelled super good! But then it hurt really bad.

Hope it heals fast.

Enjoy your WELL DESERVED holiday!

I found this while browsing at work sure looks cool.

its a Atmel AT90CAN128, so it has CAN, RS232, I2C, 128kb and can be spec'ed up to include an SD card module. with case. I think i just found my display interface for the car! will be much like the Apexi PowerFC Hand controller. We could use these to configure the open source controller, charger and BMS, as well as display with various modes. The setup would be <$200USD. VERY cool IMO.

I spent a bit of time reading up on CAN. I can't wait for CAN and the modularity it will provide, as its exactly what i've been waiting for...

adamj12b · 03-24-2010, 09:15 AM

Quote:

Originally Posted by MPaulHolmes

I don't have a motor/coupler/anything that can really test 1000 amps safely.

Wrong!! Your batteries will laugh at discharging whatever a 1000A controller can use!!

Those Diehard Platinum batteries are Odyssey's . They will do 1750A for 20 seconds!!

Quote:

Originally Posted by jackbauer

Paul quick question. Would it be possible to program the controller to limit the motor voltage?

I take it your thinking of adding those other 2 batteries? LOL

Basically all you need to do to limit the motors voltage would be the duty cycle. So an idea that pops into my head would be limiting the throttle range.

So right now you have 96V. The 2 other batteries would bring the voltage up to about 120V. So you will need to limit the pwm to the difference between 120V and 96V. So 120/96 = 1/25. 511/1.25 = ~409. So if you increase the value(lower number) of max throttle, t-min-rc ###, so that with the pedal to the floor, decrease the t-min-rc number till PWM max's out at 409. This will limit your 120V battery string to 96V.

-Adam

MPaulHolmes · 03-24-2010, 09:15 AM

Awesome!
Eat what you CAN, and what you CAN'T you CAN...

One of the things I like about CAN is that various nodes can come in and out (actively unplugged and plugged in) and the network doesn't care unless you tell it to care. Oh man, I have to go get on an airplane! Joe wrote, so we'll try to meet up with him! ya! That will be fun!