Paul & Sabrina's cheap DIY 144v motor controller

[DJBecker]

Originally Posted by wakinyantanka

IXYS makes these; IXFN230N20T. I think they will work nicely. At least I hope so.

OK, I see Digikey has these, although they are $25 each instead of $7.74. That's a pretty hefty bump in price.

[mora]

Originally Posted by emeded

Did anybody try this controller with the Kostov 9" motor? I assume there should not be a problem as this is series wound motor as well.

Originally Posted by mora

Hey, I have 9" Kostov but it is still in its wooden box, hehe. I still need coupler back from the machinist. I also use P&S's controller. Any DC/series Kostov should be fine with this controller. I suppose those will also perform pretty well as most of their motor test data goes over 500A at 144V.

I finally got (almost) everything set up and tried the motor in real-life conditions. Runs well and pulls good if I command it to do so. I've limited battery amps to 300, current ramp rate to 20 and kp/ki set to 8 and 20 if I remember right. I'll need to check all the other values next weekend when I get to drive the car again. Values might still need more tuning. I'm using 96V/90Ah Thundersky-pack.

Controller works great. It reacts immediately to throttle pedal and feels really smooth. I connected a laptop to controller using Deltaco-branded usb-serial -adapter and used RTD Explorer for monitoring and setting all the parameters. On -15C day I managed to get heatsink temperature to -6C after driving for a while. Now I need to run that serial cable through firewall and have some driving data logged.

[wakinyantanka]

Originally Posted by DJBecker

OK, I see Digikey has these, although they are $25 each instead of $7.74. That's a pretty hefty bump in price.

Yes, much more expensive. For me though there are some advantages that I'm willing to pay for.

[shortcircuit]

Originally Posted by DJBecker

You'll likely find the Arduino hardware easier to start with.

The Arduino boards use the Atmel ATMega AVR processor family, the same type as the Cougar. You won't need most of the hardware on the Cougar board, and the Cougar firmware will run on any of the Arduino boards with only a few minor changes.

The bonus is that there are many plug-in "shield" and "module" boards for Arduino cards, so you can often do projects just plugging them in rather than doing modules.

THANKS DJ!

I was thinking of the Arduino because I saw a shield that would read an SD card (and give me some memory for variables like ramp-up speed, and maybe even thermal cutout time)

'course I could also use it to do something *Really* stupid, and make it "self-reprogram" I.e. if I should make changes to the code, simply name it something specific. then the old program could write the new one to the microcontroller! kinda like firmware revisions.

I think this could be marketable...

[DJBecker]

Originally Posted by shortcircuit

THANKS DJ!

I was thinking of the Arduino because I saw a shield that would read an SD card (and give me some memory for variables like ramp-up speed, and maybe even thermal cutout time)

The software to read and write SD cards is a bit complicated. You'll definitely want to use one of the processors with more memory, and a pre-written library.

You won't be able to run programs from the SD card. Programs have to be first copied to the internal flash, which is a pretty slow process.

The Arduino boards all come with a small bootloader program that runs right after reset to check if you want to download a new program. If there isn't a download request, it jumps to the user program. This works pretty well for updates, but you do have to check that it won't screw up your control. The bootloader sets all of the OCR1A/B/C pins to outputs, which might command full throttle for one or two seconds.

The AVR processors all have small EEPROM memories which is where operational parameters are usually saved.

[shortcircuit]

Originally Posted by DJBecker

The software to read and write SD cards is a bit complicated. You'll definitely want to use one of the processors with more memory, and a pre-written library.

You won't be able to run programs from the SD card. Programs have to be first copied to the internal flash, which is a pretty slow process.

The Arduino boards all come with a small bootloader program that runs right after reset to check if you want to download a new program. If there isn't a download request, it jumps to the user program. This works pretty well for updates, but you do have to check that it won't screw up your control. The bootloader sets all of the OCR1A/B/C pins to outputs, which might command full throttle for one or two seconds.

The AVR processors all have small EEPROM memories which is where operational parameters are usually saved.

so my best option is to simply use a USB arduino to make programming/reprogramming easy....
THANKS!

[flores]

One question about the thermal isolation..

Would it be better or worse to use the thicker isolation pad of 0.020" ?
These are more expensive.. does that mean better?

[MPaulHolmes]

I think it's safer from accidental poke-throughs, but worse heat transfer. So, if we are just really really careful about making the heat spreader mirror smooth (I plan on milling flat all of the heatspreader faces, which I don't normally do), and clamp the mosfets and diodes down, I think it will be fine.

[DJBecker]

Originally Posted by flores

One question about the thermal isolation..

Would it be better or worse to use the thicker isolation pad of 0.020" ?
These are more expensive.. does that mean better?

Isolation pads come in different thicknesses using the same material. Thicker isolation pads have worse heat transfer, but it's not linear with thickness. You can end up with better thermal performance with a thicker pad when you have irregular surfaces.

Not all thermal sheets are the same -- there is a huge difference in conductivity, and you generally pay a lot for the better materials. If you need the best... well, they know you *really* need it and price to match.

[twotires]

I got a sample of thermal gap pad .... but it's only 4 in X 4 in - would it be OK to cut 20 mosfet-sized squares and only cover the backs of each device?