CompuPro floppy controller differences

dwight elvey dkelvey at
Sat Sep 23 12:10:35 CDT 2006

>From: Allison <ajp166 at>
>I also have a smaller version that runs from 12V battery for smaller
>motors to 30watts.  Most motors tolerate a squware wave source so
>efficientcy can be very high.  The trick of running AC motors off
>variable frequency also is used for my antenna rotator (ham radio) so
>I can make large changes in azmuth with acceleration and deceleration
>as most rotator are AC motors and the antennas have some interta
>(15 and 18 foot booms).  This also has a microcontroller (8749) to
>manage the position and motor controls.
>Doing it with a solidstate converter is far more efficient than motor
>driven alternators for frequency conversion at low power. Much quieter
>too.  I've since seen the same thing for done for large (10hp and up)
>motor controller.

A friend has an older Celestron telescope with an AC clock drive.
We took one of those 12v to AC converters and added a couple pots
and switches to vary the frequency for tracking the telescope while
doing photo work. The converter used simple 555 circuits to control
the frequency so it was relatively easy to modify.
It is often much simpler to modify one of these than to build something
from scratch. One does have to be careful, the capacitors can have
nasty voltages on them.

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