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Old 02-05-2008, 10:09 PM   #1 (permalink)
Nomadic Chicken
 
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Home Brew Challenge for Electric Geniuses (make a DIY electric motor controller)

You know what would be really cool? ....

This friday i will likely be spending less than $100
on a very large motor. But to get my EV to go far
and fast enough to make me happy, I will have to
learn about batteries and Controllers...

The dollar markup on Motor controllers that handle
large volts and amps is amazing. Most likely, if you
built one yourself (programmable or not) then you
would save more than 1/2 the money. (simple
supply/demand for large controllers is probably the
biggest reason for the cost)

What would be really cool is if some brains on this
forum came out with an open source controller that
you could build using electric parts bought from Radio
Shack or Fry's Electronics that can serve EV means.

For those of us hoping to build or convert a vehicle
to EV - or to add in a electric motor for home brew
hybrids - the cost savings would be enormous.

Also, by having something such as this open source,
new members who are electrically inclined may decide
to attempt to improve the design once they join resulting
in multiple versions that eventually would be sufficient
for what ever an EV Builder's needs may be.

Now, as most of you aware, I know crap about electricity.
(i'm still considering taking a little 12v motor i pulled out
of a toy car and hooking it up to my car's battery to see
how long it can last on 500CCAmps)

Now that I've tossed the idea out there (i mean, for a home
brew EV Motor Controller. not for blowing up a toy motor)
I would like to know if anyone in the community would like
to step up and consider tackling this challenge (either alone
or with other forum members) to make this a reality.

While you consider, here are some example links I found for
smaller controller schematics and information that may be
useful:

Link 1
Link 2
Link 3
Link 4
Link 5
Link 6
Link 7

Will anyone step up and attempt this challenge?

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Old 02-05-2008, 11:33 PM   #2 (permalink)
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I don't want to be a naysayer. OK, yes I do! No. Really...

But the largest assembled brain trust on the subject of EV's is the Electric Vehicle Discussion List: http://evdl.org for info.

The subject of open source home brew controllers comes up every other month on the list, usually suggested by someone who wants to do a conversion, but doesn't want to (or doesn't have the means to) fork over the beans for a commercial controller.

In the 2 years I've been reading posts there, nobody has yet made one. The challenges are serious, when you consider the job a controller has to do and the environment it has to do it in, and the consequences of something going wrong with it while & where it's being used.

And it's not for lack of smarts. The number of really smart people on that list is astounding. The fact that a bunch of really smart & experienced people haven't yet made an open source controller that anyone can build for less money than a commercially produced one tells me something.

Not saying it can't be done. But since I'm not an EE with time to spend on the problem, instead I continue to haunt eBay regularly watching for a bargain on the unit with the specs I'd like to have...
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Old 02-05-2008, 11:36 PM   #3 (permalink)
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And BTW, you don't necessarily need to start with a PWM controller. Electric vehicles of all sorts used contactor controllers for most of last century before the solid state electronics came along to do the PWM magic.

Have a look at Ryland's Citicar thread for info on that type of controller.
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Old 02-05-2008, 11:43 PM   #4 (permalink)
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No offense taken from your NaySaying.
BTW, when I buy/find a working controller, I plan to
open the baby up and - if permitted by the various
EM Mods here - post up a schematic of how it works.

If nothing else, maybe it'll be a good starting point
for people to home brew on the subject (if there
isn't already an Open Source controller posted up
by then.)

I just find that paying up to $2000 for a controller
to be disgusting when they are made by employees
who are only paid $0.50 an hour in china.
(or some other ridiculous number)

EDIT: we were both posting at once.
Yes, That is one thing i'm looking into.
Infact, an open source contact controller
schematic is one of the links i posted up.
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Old 02-05-2008, 11:51 PM   #5 (permalink)
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What are the specs required for a PWM controller?

I have built PWM systems for a few things, I have built computerized nitrous controllers, r/c car stuff, and other dc motor controllers. The PWM part is easy, The high current capacity can get expensive though. But it should still only be a few hundred bucks even for some really expensive mosfets.
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Old 02-05-2008, 11:57 PM   #6 (permalink)
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Quote:
Originally Posted by WaxyChicken View Post

I just find that paying up to $2000 for a controller
to be disgusting when they are made by employees
who are only paid $0.50 an hour in china.
(or some other ridiculous number)
Hey now... I got to meet Otmar [insert last name] - the guy that designed/builds the Zilla controller... From what he said, it sounds like all of the mfr'ing is done in house and by hand (I believe they still have a 6 month waiting list) Hell, they even go so far as to "pair" IGBT's into sets so one doesn't fry before the rest due to slightly differing tolerances... That's some awesome QC - and one of the reason's why people are willing to pay $2K
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Old 02-06-2008, 12:05 AM   #7 (permalink)
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Quote:
Originally Posted by Coyote X View Post
What are the specs required for a PWM controller?

I have built PWM systems for a few things, I have built computerized nitrous controllers, r/c car stuff, and other dc motor controllers. The PWM part is easy, The high current capacity can get expensive though. But it should still only be a few hundred bucks even for some really expensive mosfets.
Let's give you an example.
(looks around and finds the motor that didn't work)
Quote:
General Electric
Mod: 5BC 48 JB 711
Rpm: 1600
HP: 1
V: 12
A: 87
Time Rating: 60 Min
Amb Temp: 40C
Ins Class: B
Wound: Series
FR: 48
GEJ: 3122
Serial No: MXN
Fort Wayne Indiana
N.E. 180051 EA
that's a simple 12V 87Amp 1600 RPM motor. Maybe good enough for a 3 wheel trike (if the motor suddenly decides to work or if i rebuild it)

Just as an example - that motor on the controller's output
with 2 car batteries in series equaling 24 volt 750Amp DC input
(a ballpark of car battery amps)

could you do something for a motor like that?
(no shame if you say it's over your head.)

Myself, i'm getting a larger motor this weekend so the controller wouldn't be much use to me. but it'd be a good test for you to see if you can figure it out.

edit: LINK this is a simple PWM controller for a small fan.

Last edited by WaxyChicken; 02-06-2008 at 12:19 AM..
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Old 02-06-2008, 12:26 AM   #8 (permalink)
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87 amps would not be that hard but 750 amps would take some really big wires I thought most electric cars had stuff like 4ga wires going to the motor. With that many amps it would need something like 00ga.

Ill have to look around and see what I could do to make a fet bank that can handle 750 amps. That would be probably big and a pain to build for a normal hobby type of thing though.
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Old 02-06-2008, 12:44 AM   #9 (permalink)
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I could be wrong, i've never completed an EV Before and am still collecting parts for my first attempt.

Image from EVA/DC
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Old 02-06-2008, 12:57 AM   #10 (permalink)
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I have some experience with RC PWM controllers but nothing in the realm of what you're talking about with that kind of current. In theory the design would be the same though, just with more robust parts really. It would seem that you could almost just reverse engineer an RC controller and find higher tolerance parts to substitute in for the ones in the existing schematic...no?

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