From: firstname.lastname@example.org (Glen Walpert)
Subject: Re: large (5HP) DC motor controller design issues
X-Newsreader: News Xpress 2.01
Date: Sun, 29 Sep 2002 23:58:20 GMT
NNTP-Posting-Date: Sun, 29 Sep 2002 19:58:20 EDT
Organization: Net Access (netaxs.com)
In article , "Richard Everett" wrote:
>I agree that it would be nice to repair the old drive. Unfortunately, there
>are no schematics, manuals, or any other info on this 1980 vintage drive.
>It is quite complicated...if I reverse engineered it, I would probably
>deserve some sort of award.
>Here are pics of it to give you an idea:
>Pic of the overal spindle driver boards (note the size of this beast!!!)
>Pic underneath the right side board (on hinges)
Hard to tell much from the pictures, I can't even see the power semiconductors
let alone read their part numbers.
>Still, I guess it is an option...some of the chips are way obsolete though,
>and even getting data sheets for them is hard. Plus, there are a few
>proprietary chips from the spindle manufacturer.
Do not try to reverse engineer the entire schematic. Start with a sketch of
the main power path, from line in to the motor terminals. If you can't find a
data sheet on the power semiconductors it uses, look for something similar
from the same manufacturer. Then figure out where the gate drive comes from -
I'll bet the row of a dozen little transformers on the left board in your
photo provide gate drive isolation, and there are a dozen power semi's below
that board. All the gate drive circuits will probably be the same. Then find
the DC power supplies for the controller, follow the traces from the power and
ground pins from a chip you have the pinout of, perhaps. Identify test
points, including all control inputs to the controller from panel switches,
CNC processor, whatever runs it. Power it up, what happens? Are all the
inputs there? Power supply voltages OK? Logic level gate signals there?
Isolated gate signals there (careful, not ground referenced!)? Power semi's
Even if you find that the problem is in some proprietary controller chip you
have no hope of figuring out, if you can figure out the power section you have
a darn good start on building your own drive, all you will need to design is
the the low power low voltage control electronics. I'll email your award :-).