Re: [CAD_CAM_EDM_DRO] Idea for PWM to analog speed control

On Thursday 29 April 2004 09:14 pm, washcomp wrote:

> I came across a source (for $2.00 each) of:
>
> The uA7392 is a 14 pin IC that is designed for precision, closed
> loop, motor speed control systems. The motor speed is determined by
> frequency to voltage conversion of the input signal provided by the
> tachometer generator. The result of the comparison controls the duty
> cycle of the PWM switching motor drive output stage. With data.

This sounds awfully familiar. And I'll bet it resembles another chip, the
part number of which I can't remember, that was used in certain models of
floppy drive. You could always tell when there was a problem in this area
because the motor would run *way* faster than it usually did (300rpm).

The motor in question had four wires, two for drive and a "tachometer"
winding. That latter winding opening up was the cause of the problem when
there was one, usually.