Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

That's a really good idea to delay stuff and make money haha! Well, I decided to OFFICIALLY ORDER THE 3 BOARDS!!! I had just enough to get it now, and when the stupid random bills come due, the paypal money should be there! ya!

They say it takes about 1 week for them to get around to doing their weird think to make the pcb's all etchy. Then, their shipping (from Australia) takes.... gasp... 1 to 2 weeks. Let's just say I'll be doing some power section etching and drilling, copper heat spreader drilling (yuck!), bus bar drilling, Bus bar TINNING (HOW AWESOME IS THAT?), and any other dookie that I can't think of right now. Then, when they get here, there won't be as much to do.

Matt, I wrote to them and asked about your questions, and Bee wrote back and didn't answer that part of the email... Maybe I should ask her again. Or maybe she didn't know.

Still need a dang blasted box. Should we just do Lexan for these 3? I need to email the guy at the Tacoma EV meeting about his quote for making a box. My intestines (my gut, actually) tell(s) me that his would be expensive, though. He does tig welding to make his aluminum boxes. Maybe I could take some sheet metal, bend the ends and somehow make that a box? The inside electronics will be suspended from the heatsink, I think. So, the sheetmetal would have to be stiff enough to securely hold up the heatsink. Or I could have the heatsink on the bottom, and the sheetmetal box would be more of an enclosure that keeps the elements out rather than something that provided hard core structural support. Suggestions welcome!

[MPaulHolmes]

Yes, all off topic posts, except for posts that make fun of Oprah.

[Tango Charlie]

Paul
What are the desired inside dimensions of said box?

[MazdaMatt]

Australia! I didn't see that coming.

Tell me again, what is the motivation for a metal box? When someone says "tig welds aluminum" that can be loosely translated as "costs a lot of money". I am under the impression that we are trying to ensure voltage isolation from the rest of the car's systems. Last thing we need is a bus bar to accidentally touch a metal box...

For the 15 boards in the next round of testing, DEFINATELY shop around. You should be able to get much better turn-around times, if not prices, through other board houses.

Thanks for taking on the cost burden to keep this thing rolling

[diy-aviator]

Hi Paul and everyone,

Has anyone out there had any experience of Liquid cooling of Mosfets? (like immersed).
I have a hunch that it might be possible to have the fets, diodes and bus bars running submerged, and have built a small test rig (plastic box and 2 fets) to test the idea.
Problem is I have no idea what to use as coolant. I tried light oil but the temperature coefficient was disappointing.

Ideal fluid would have the following properties:
Non conductive to 500 volts.
Good thermal conductivity.
Non volatile or flammable.
Inert and non destructive to plastic package semiconductors.

If anyone has any suggestions as to what might be suitable, I would be extremely
grateful.

Regards, Mike H.
(diy-aviator)

[charlie_fd]

Australia ?! Any connection to zeva.com.au ?

[taffy]

Were about in australia i have to ask? Want me to drop round and "ask" them to hurry up.

[vinny1989]

Originally Posted by diy-aviator

Hi Paul and everyone,
Has anyone out there had any experience of Liquid cooling of Mosfets? (like immersed).
I have a hunch that it might be possible to have the fets, diodes and bus bars running submerged, and have built a small test rig (plastic box and 2 fets) to test the idea.
Problem is I have no idea what to use as coolant. I tried light oil but the temperature coefficient was disappointing.

Ideal fluid would have the following properties:
Non conductive to 500 volts.
Good thermal conductivity.
Non volatile or flammable.
Inert and non destructive to plastic package semiconductors.

If anyone has any suggestions as to what might be suitable, I would be extremely
grateful.

Regards, Mike H.
(diy-aviator)

Some computer enthusiasts have submerged their entire PC (except hard drives, CD drives and Power supplies) in mineral oil with no problems.

But a controller such as Pauls design is running on much higher volts and amps than a PC, im not sure what would happen.

However, using normal water cooling, with pipes and heat-transfer-heat sinks (I don't know the correct name), could work well.

[MPaulHolmes]

No connection to zeva (Hi Ian!!!).

Here's the information for futurlec:

Futurlec
2/136 Broadmeadow Rd
Broadmeadow
NSW 2292
Australia
FAX Number – Local : +61 2 94 75 4051

If you need further information, please do not hesitate to contact us.


Best Regards
Bee
Sales Assistant
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Ya, Australia came as a bit of a shock to me too! haha! Plus, I'm allergic to Bees, and I've been communicating with one over email. That's playing with fire, man...

Hey! A friend of mine had a really sneaky plan for cutting production costs on the control board. Eliminate the silkscreen, and just have the information like "R18" etched onto the board! Then I believe they tin the whole dang copper afterwards, which could then eliminate the need for the soldermask? Then it would cost like 1 penny each!
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I've been reading up on the AT90PWM3b, which is a $4 Atmel microcontroller that is specifically designed for things like AC controllers, brushless DC, synchronous rectification, Only doing A/D sampling while not switching, center aligning of who knows what, etc... Pretty much all the programming of the ATMega8 16 32 is transferable to it.

The synchronous rectification (which is straight forward-ish to implement on the AT90PWM3b) may not offer much in the way of heat savings, but it replaces a diode that can handle 50-60 amps RMS with a "diode" (mosfet) that can handle 120 amps RMS. Now the mosfet can't REALLY handle 120 amps for very long, but I bet it could do maybe 75 or 80! That would make a 750-800 amp controller with only 10 mosfets and 10 "diodes" (where the diodes are actually mosfets).
It's only in the surface mount type, though, so if we have a version that is all surface mount, that might be a fun thing to try! The one guy that I forgot the name of said his friend could help with doing the surface mount soldering with that weird machine that can do like a gazillion soldering things every second!
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TANGO CHARLIE:

INSIDE BOX DIMENSIONS: For monster motor man (ben), I'd say 7"x3"x10.5"

For Yo! (Adrian) and the phoenix fireball (joe), I'd have to say
6.5"x3"x9.5"

Maybe we could get away with 2.85" tall inside, but I don't know. The method of mounting the control board to the underside of the power section is in the air, so the height is a bit in the air. Little details here and there. Holy cow that rhymed!

[ev59rag]

I believe that the wait is only true for paypal if its attached to a savings account. But if its attached to credit card, then the purchase has no waiting.