Re: Servo amp connections needed. Where should I go from here?

Thanks Jon,
That is what I was afraid of. Now the problem is finding that info.
There is an encoder mounted on this motor. I don't think it's
possible to get the velocity feedback from it. I think it's 5v but
then again the tach input may be scaleable.

DC

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> sleyed wrote:
>
> > Hey Thanks Chris,
> > There is no tach on the motor I am using.This is a mishmash of
> > parts.I was trying to simulate the tach input at the same time as
the
> > signal hoping it would null out somewhere near zero volts on each
> > input.
>
> This will not work. There is essentially an open-loop op amp in
there,
> comparing actual to commanded velocity. You MUST have a valid
> velocity input, or else remove this servo loop from the circuit.
> (Some servo amps have a jumper to do this.)
>
> > It may be a case where I need a slight negative to null it.
>
> You can't null an open-loop amplifier. The gain is too high, a
fraction
> of a mV drift will cause it to swing full scale.
>
> > You are correct in stating there is a + and - 10 voltDC
terminals.
> > I was considering putting a 2k pot as a variable voltage divider
> > across these +/- terminals to get a 20volt spread with 0 volts at
> > center.Then using the pot wiper as the output to the signal
>
> Yes, that will work fine.
>
> > and tac
> > inputs respectively.
>
> But, as I say, you either need the tach feedback to close the
velocity
> loop, or you need to deactivate the velocity loop. That will take
info
> from the manufacturer.
>
> Jon