Re: [CAD_CAM_EDM_DRO] Another Solution!!!!To convert Quadrature Encoder signals to Tachogenerator signals

Hi All,

I was in the process of developing the circuit
suggested by Jon to convert Quadrature Encoder signals
to Tachogenerator signals, when this new idea striked
me,
The idea is that , Can I use a small Dc motor ( used
in CDROM drives or tape recorders) in place of
Tachogenerator. Due to the samll size of these motors
it is easy to make the mechanical attachment for
connecting with motor. Regarding the output voltage, I
think an OP-Amp can be used for scaling.

But before start working on this idea I want to ask
the experts if this idea workable?
Please advise..

Regards

Babar
--- Jon Elson <elson@...> wrote:

> Jon Elson wrote:
> Arrgh! Try it again with fixed-space font:
>
> >Babar wrote:
> >
> >
> >
> >>Yes , my aaplication is a DC servo motor for
> X-Axis of
> >>a turning center .Actually the motor and Drive
> >>(A20B-0007-0361) are both from Fanuc , The Drive
> have
> >>3 different modes of operations:
> >>
> >>1) Tacho 3V
> >>2) Tacho 6 V
> >>3) Pulse Encoder +F/V
> >>
> >>In my machine the servo motor does not have the
> Tacho
> >>and the drive was running in 3rd mode, the F/V
> logic
> >>was implemented in orignal CNC control, which I am
> >>replacing with Powerautomation GmbH CNC control.
> >>
> >>
> >>
> >Oh, we KNOW about this one! We ran into the same
> thing on
> >the Mazak conversion at Roland Freistad's. The
> servo amps
> >(Fanuc A06B, I vaguely recall) were velocity
> servos, plain.
> >The CNC control generated signals to simulate the
> tachometer
> >feedback, and sent this to the servo amp.
> >
> >I'm not sure exactly what the group did to solve
> this problem,
> >but they apparently got a F/V converter that was
> made for
> >exactly this purpose.
> >OH, I finally found it, they changed out the amps
> to Servo Dynamics.
> >I still think they could have used the old ones,
> but the first machine
> >had phase-control SCR drives. UGH! Those SHOULD
> be changed!
> >See more detail than you want at
> >
>

http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?MazakRetro

> >
> >
> >
> >>Pete and Jon Elson are right about using the F to
> V
> >>circuit, The main problem for me is how to convert
> the
> >>sign of the analog voltage generated by the F/V,
> Jon,
> >>you have recommended some "Linear inverter"
> >>
> >>
> >>
> >This is a simple op-amp, with a switch to flip the
> polarity.
> >I will attempt ascii art here :
> >
> >
> >
> >
> >
> ----/\/\/\/\--
> > |
> |
> > R R | |\
> |
> >Input -------/\/\/\/\-----/\/\/\/\------ |-\
> |
> > | | | \
> |
> > | A o |
> \-------- Output
> > | R/2 R/2 | /
> > |-/\/\/\/\------/\/\/\/\---------|+ /
> > | | | /
> > | | |/
> > o | R |
> > B |--/\/\/\/\--|
> | . (Gnd)
> > |
> >
> >
> >In this circuit Ressistor R are all same value, R/2
> are half that value.
> >When circuit point A is grounded, the amp is
> inverting, when circuit
> >point B is grounded, the circuit is non-inverting.
> You need to set
> >up MOS switches to do this grounding.
> >
> >
> >
> >>and
> >>"quadrature to step/direction converter "
> >>
> >>
> >>
> >Here's a circuit right in our own files section. I
> put in the
> >triangle brackets, so hopefully the link will work
> right :
>
><http://f1.grp.yahoofs.com/v1/EBfRQ7c69mR-gvi4N1lI3XKhUbRmzFzc6htQVHMMV09BeMrVGS3RqYn-Mc4cpyQKnuJc11ymfTUWxYdX2oNB0zOGIIbW/CIRCUITS/Pulse%20Gen%20%20and%20Timing%20Circuits/Quad2StepDir.pdf>
> >
> >
> >
> >>for this
> >>purpose ,could you please give me some link to
> where I
> >>can find these circuit schematics?The Pulse coder
> >>installed in the motor is of 2500 cpr.
> >>
> >>before this discussion ,I myself was planning to
> use
> >>the drive in mode 1 or 2 and for this purpose to
> use
> >>2 F/V ICs with a 4066 analog switch for the sign
> >>conversion of the analog voltage, but I don't know
> >>whether this circuit will be fast enough to meet
> the
> >>servo's requirement.
> >>
> >>
> >>
> >>
> >>
> >Yes, it should. The problem is there will be a
> discontinuity between
> >the two signs, which will cause instability at
> (near) rest. that's why
> >one circuit bot both directions is better. You put
> the smoothing after
> >the sign inverter. The 4066 swich is fine, but
> needs to be run from a
> >-5 +5 Volt supply so it can handle the range of
> analog signals. Then,
> >the signals to command the switches need to be
> level translated to
> >+/- 5 V levels (one transistor for each switch).
> >
> >Jon
> >
> >
>
>
>
>
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