On Mon, 26 Aug 2002, Donovan Parks wrote:

>I'd be very interested in these sensorless ways of obtaining feedback.  Can
>you elobrate or point me to some resources?

The motor is also a generator and if you turn off the drive momentarily
and measure the voltage you have a pretty accurate assessment of rpm. This
happens too fast for the motor or the load to notice. It is also possible
to do this without interrupting the voltage at all in a linear driver.
This is harder to explain but it works on the same principle (except it
also needs to know the dynamic internal resistance of the motor). The
speed regulated cassette tape (walkman) motors almost all use this
principle (excepting high end units which have tachos and/or are
synchronously driven by a mcu).

Peter

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics