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

As a previous post said the gain of the input amplifier will be quite high
so even a small input signal will have the effect of driving the amp to
saturation. Under normal circumstances the tach signal is of the opposite
polarity to the input signal and the difference between input and tach is
very small due to this high gain amplifier. Sometimes you can degain the
input amplifier with a jumper or resistor so that you have a low gain on the
input. Even using the ideas in your post the amplifier will have limited
control due to the high input gain.

Regards Peter

----- Original Message -----
From: "sleyed" <Sleyed@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, January 29, 2002 6:46 AM
Subject: [CAD_CAM_EDM_DRO] Re: Servo amp connections needed. Where should I
go from here?


> 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. It may be a case where I need a slight negative to null it.
> 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 and tac
> inputs respectively. Without the book it will be difficult to
> determine what the polarity should be other than a common is nearest
> the tac input. The only problem I see here is the 20volts seems a bit
> high for the input signal. Not out of line for the tach if 7v=1000
> rpm so 20volts would be 3000RPM.
> There are also some pots on the board. The obvious ones are for
> current limit and servo response. The other 3 have something to do
> with the inputs of the signal and tach sensativity. They are only 1/2
> turn pots. Not like the 10 turn pots on other amps I have tuned in
> the past.
>
>
> That is about all I have to go on.
>
> DC
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., ccs@m... wrote:
>
>
> >
> > You need to hook up the tach to a tach on the motor, getting the
> > polarity right (ie, if it takes off swap the tach or motor wires)
> and
> > then try putting an analog command voltage into the input. There
> may
> > a pot you can tune for a slight offset, but you will really need to
> > find positive and negative supplies if you want to run it with a
> > pot... you ight be able to find the voltages in the drive somewhere
> > to borrow for testing purposes.
> >
> > Chris
> >
> > > I have a servo controller that I can't seem to find any
> information
> > > on.
> > >
> > > It is manufactured by Control Systems Research, Inc. Pittsburgh,
> PA.
> > >
> > > The model is NC121F.
> > >
> > > My question is in trying to get control of a servo motor with a
> > > single or stacked potentiometer.
> > > The controller has signal and tac inputs. I do not know what it
> is
> > > expecting at these inputs. My first guess was 0 to +10v at both
> > > terminals in relation to the common. I don't really have 0 to -
> 10v so
> > > I am unaware if a null point could be reached this way.
> > > My mode of thought here is that the tac may output 6-7vdc/1000
> rpm.
> > > If the inputs were tied together then they would track each
> other.
> > > Not so, or at least it did not prove out.
> > > When I touch either the tac input or the signal input with one
> wire
> > > or my fingers. The shaft slows and stutters . Possibly the stray
> ac
> > > signal I presume from my overhead lights. Using another power
> source,
> > > it was found to reverse the motor direction by connecting the
> signal
> > > lead to ground.
> > > Am I way off base in my mode of thought for bench testing this
> > > setup?
> > >
> > > DC
> > >
> > >
> > > Addresses:
> > > FAQ: http://www.ktmarketing.com/faq.html
> > > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> > >
> > > Post messages: CAD_CAM_EDM_DRO@y...
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> > > bill,
> > > List Manager
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
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> > >
> >
> > -------------------------------------------------
> > Christopher C. Stratton
> > Engineer, Instrument Maker, and Horn Player
> > ccs@m... 617 628 1062
> > http://web.mit.edu/~stratton/www/brassbuild.html
>
>
> Addresses:
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>
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