SNIP
>
> I have limited knowledge and experience with electronics, but here is
> some of my recent experience with my spindle VFD.
>
> Just for testing, I used a parallel port out put with an RC filter and
> found that to smooth the signal, the capacitor had to be quite large
> which also slowed the signal response. So, if you command a 100% to 0%
> speed change the filter output will actually take time to go from 10
> Volts to 0 Volts. Contributing factors to the large capacitor are; the
> parallel port's PWM frequency is fairly low and the VFD input is a high
> impedance input. My test actually worked okay but it seemed that I could
> not make speed changes fast enough to get the VFD to utilize dynamic
> braking. I was hoping for an order of magnitude better performance, so I
> didn't pursue this any further. (Are there better "active" filters?)
SNIP
>
> Kirk Wallace
>
Doesnt EMC have a PDM output option?
This would be _much_ easier to filter than PWM.
With PDM a ~.1 second time constant filter should be fine
>
Peter Wallace
Mesa Electronics
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