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

>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
>
>