On Mar 30, 2005, at 2:41 PM, Lindy Mayfield wrote:
>
> Actually I'm scavenging for things for robots...

Older, slower CD drives (and probably STILL audio CD drives that
only need to run a '1x' speed) used normal DC brushed motors for
the spindle.

Higher speed spindle motors on CD and HD drives are usually three
phase brushless motors with hall sensors used for feedback to
create the proper drive waveforms (not so much exact speed control,
although that follows as well.)  Most of the ones I've seen have
the three phases connected in either Delta (3 connections) or Wye
(4 connections), with additional connections for the hall sensors.
In the drive, these motors are drive by high-integration wonder
chips that connect to all the pins on the motor, plus assorted
inputs from a microcontroller, plus (frequently) other outputs
for the other motors and things in a typical drive.  Most of
the drives I've dissected use Rhom chips that are particularly
hard to find spec sheets for, especially if they're not the
"current" generation, but here's a representative sample:

http://www.semiconductors.philips.com/pip/SA56203STW_N1.html

Power to each coil seems to be on the order of an amp.  I have
not seen simple circuits to do anything useful with these motors,
but it ought to be possible, I keep thinking, even if it is in
somewhat "jerky" stepper fashion... I also haven't been very
successful using the original driver chips to drive the motors;
they seem to require quite a bit of 'housekeeping' or something...

Now, if you're into remote control, there's a whole movement
in taking these spindle motors and turning them into high power
brushless motors for driving your propeller in an electric plane.
This requires a controller of considerable complexity or expense
(>$50 for commercial units), but is getting wonderfully documented:
http://www.rcgroups.com/forums/showthread.php?s=&threadid=127606
http://www.gobrushless.com
All you do is replace the magnets, rewind the coils, put in better
bearings...  These guys are crazy, but they're getting performance
equal to $60 motors from $10 worth of parts and some time.

Let us know if you discover anything particularly interesting...

BillW
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