At 05:21 PM 11/21/02 -0500, 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? If this is something like a treadmill motor, all you should need is a phase controlled full wave bridge rectifier (2 diodes, 2 SCRs) operated directly from the 120 Vac line. This is how most tread mills do their speed control. The 90V rating on the motor comes from full wave rectifying the incoming 120 Vac but not filtering it; and operating a somewhat less than the full 180 degree conduction for each half-cycle. Most older blueprint machines use similar motors (smaller, of course) and control techniques. For a simple test, just grab a fan-motor rated speed control and connect it to a bridge rectifier feeding the motor. Should work just fine. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.