Take a look at http://www.robot-power.com/ and the Open Source Motor Control
(OSMC).  They have the design published for a PWM power unit that is a  160
A, 50V H-Bridge.  They supply both the schematic and a kit.  I purchased the
kit and assembled it with no problem.  Unit works good.  While you  may not
want the kit, the schematic should help you design what you need.  The PWM
control is from an Intersil HIP4081PWM controller that controls external
FETs for power.  I used it in another project (zero shift focuser for my
telescope).

David V. Fansler
DFansler@MindSpring.com
www.DV-Fansler.com

 -----Original Message-----
From:   pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]
On Behalf Of Lucas Thompson
Sent:   Thursday, November 21, 2002 5:51 PM
To:     PICLIST@MITVMA.MIT.EDU
Subject:        Re: [OT]: Need ideas for supply for 90V motor drive....

I'm looking for nearly the same thing but for a 30-volt, 15-amp
reverse capable PWM speed controller for brushed-DC permanent
magnet type motors. The +-30V is going to be supplied by a big
ni-cd pack.
I've looked around on the PIClist site and found some promising things
but they seem to lack reversability. Ideally, it'd be able to brake the
motors with a PWM-to-ground short circuit type mechanism instead of
trying to apply opposing voltage to get the motors to stop.

Maybe someone else has already done this exact thing. Gladly take any
suggestions!

Chris Loiacono wrote:
> Once again, I'm not looking for anyone to do my work for me - just
> hoping someone can give me a little push down the hill. I'm after the
> lowest cost way to make the 90V needed for a brush motor PWM speed
> control w/ current limit.....Any ideas as to where I might start
> looking?

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