At 11:41 AM 5/26/03 +0100, Brian Clewer wrote: >One thing to think about here is that when the AC voltage is rectified, the >DC voltage goes up by a factor of root 2 (VAC X 1.4142). Therefore, 120 VAC >goes up to approx 170 VDC - you might want to up rate the DC motor to suit. This happens only if you have sufficient filter capacitance after the rectifier. Most DC motor speed controls I have seen don't use filtered DC, but rather use 2- SCRs and 2 diodes to make a phase controlled bridge rectifier. Average motor voltage varies between 0V - 105 Vdc. For what its worth, have a look at the surplus treadmill motors available. Those are usually rated at 90 Vdc. Same phase controlled bridge to drive them - just don't allow 100% conduction. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 19 years of Engineering Innovation (1984 - 2003) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' 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: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu