Stepper AND Servo

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07 Nov 2012 16:10 #26331 by Chibo
Stepper AND Servo was created by Chibo
Hello,

this is my first project with LinuxCNC. I'm a mechanical engineer with some electric knowhow, but I'm not a software expert. So i would be very happy, if you could answere me a few question.

The project is a grinding machine with nummeric control. It has two steppers (Y,Z) and two servos (X,A). The spindle turns on/off by relay, so it does't work with different revolutions. There are some I/O functions (PLC) like cooling water,.... Some relays are driven with 24V and some with 230V (could be replaced).

Detail servo:
- servo motor BBC M19P
- servo tacho BBC F12T
- servo drive ELGE SD/CC
- incremental encoder Heidenhain ROD 630 (sin/cos)

Detail stepper:
- stepper motor Berger-Lahr RDM 51117 (5 pole)
- stepper controller Berger-Lahr NI 3426

So my first problem is: what hardware do I need? I think, the parallel port has not enought options.
Is the MESA 5i20 the right choice or better another modell?
Can I connect the stepper / servo controller direct to the 5i20 or do I need some daughter cards?
In this case: which daughter card or cards is the right one and is supported by LinuxCNC Mesa Configuration Wizard?
There are three 50-pin-connectors on the 5i20 - can I connect every and maybe different daughtercards to every connector I want?

Thankyou very much

Chibo

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07 Nov 2012 20:36 - 07 Nov 2012 20:37 #26335 by BigJohnT
Replied by BigJohnT on topic Stepper AND Servo
More important than the servo and stepper detail is the drive inputs. Do the servo drives use a velocity +-10v signal and do the servos have encoder feedback? Do the stepper drives take step and direction inputs?

The PLC functions are handled in Classicladder.

The 5i20 firmware determines what daughter card can plug into where. There are several combinations of firmware and a few custom ones I've seen in the past.

Another possible combination is the 5i25 plus 7i77 and a 7i76 or 7i78 depending on if you need the additional I/O provided by the 7i76.

I have in my CHNC 5i20 + 7i33TA + 7i37TA + 7i37TA setup, in my stepper driven plasma I used 5i25 + 7i76, in my servo driven BP I used 5i25 + 7i77.

I just used the sample configs and changed them to suit my machine as I prefer a hands on with the hal and ini files. Eventually you will have to modify them outside of the limits of the wizards although pncconf does some amazing things and Chris keeps adding to it.

John
Last edit: 07 Nov 2012 20:37 by BigJohnT.

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07 Nov 2012 20:50 #26337 by andypugh
Replied by andypugh on topic Stepper AND Servo

Is the MESA 5i20 the right choice or better another modell?

The 5i20 has quite a small FPGA, and can't run all the possible functions.
The 5i23 is not much more expensive, and can run much more complex firmwares.
(As an example, last night I was making myself a custom firmware for my 5i23 and could not fit in a 8 x smart-serial, 6 x resolver and 1 x 7i39 into a 5i23. I had to go down to 6 smart-serial and 4 PWM outputs.
The 5i20 is not powerful enough to handle any resolvers at all).
The 5i20 probably can handle your configuration, but I don't think it is worth the gamble that your config might not get more complex.

5i25 + extra header adaptor + 7i76 + 7i77 will certainly work, but may have rather a lot of redundant capability.

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08 Nov 2012 01:37 #26349 by PCW
Replied by PCW on topic Stepper AND Servo
a 5I25 + 7I77+ 7I78 would also likely do without so much
extra 24V I/O which is probably not needed.

But in any case the servo drive interface would need to be determined
(analog/step/dir/PWM/other)

also the Heidehaine scale may be an issue unless the interpolator
(quadrature converter) was there

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09 Nov 2012 13:33 #26396 by Chibo
Replied by Chibo on topic Stepper AND Servo
Thankyou for your answers.

At mesanet.com I have seen, that the 7i76 should be able to drive steppers OR servos. I can't find this in the manual. I would be better, if one card can handle steppers AND servos. Do anybody know, if this is possible or if any other daughtercard can handle both?

To the other unkown points (servo signal,...) I will do some homework and write again.

Greeting
Chibo

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09 Nov 2012 18:48 #26403 by andypugh
Replied by andypugh on topic Stepper AND Servo

At mesanet.com I have seen, that the 7i76 should be able to drive steppers OR servos.


It rather depends on the servos. The 7i76 can drive step/dir servo drives, but still has no way to read back the position from more than one encoder. (It has one encoder input channel, but that is mainly intended for use with a spindle encoder).
You could use step-direction servo drives in open loop mode, but then you don't really have a servo system in the way that that is conventionally understood in the LinuxCNC world.

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10 Nov 2012 02:20 #26417 by Chibo
Replied by Chibo on topic Stepper AND Servo
I know what you mean. I'm not already sure, but I think, the loop will be closed by the Heidenhain ROD's, that have to be connected to the daughtercard. The ELGE servo controller have only inputs for servo-signal (I still don't know the type of signal) and the RPM-tacho.

But what do you think about 5i25 + 7i77 and the normal parallel port to drive the both steppers? So I could save the 7i76 or 7i78. Or will that configuration make some trouble or be to slow?

Chibo

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10 Nov 2012 06:33 #26420 by PCW
Replied by PCW on topic Stepper AND Servo
You can use the second 5I25 port just like a parallel port if desired (direct connection to the step/dir drives)
but normally you would use a breakout board in between to protect the FPGA board (just as you normally use a breakout board with a parallel port for the same reason)

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19 Nov 2012 02:23 #26770 by Chibo
Replied by Chibo on topic Stepper AND Servo
Now I have it: the servo controller signal is +/- 10 Volt.

But I have another question: can I configure anything with pncconfig without having installed any mesa cards? I want to simulate the 5i25 + 7i76 + 7i77. But pncconfig doesn't show me any cards, yet.

Thanks
Chibo

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19 Nov 2012 03:05 - 19 Nov 2012 03:06 #26771 by cmorley
Replied by cmorley on topic Stepper AND Servo
Chibo

there are some hoops to jump to get PNCconf to configure for the 5i25, see here:

www.linuxcnc.org/index.php/english/forum...ml-files-for-pncconf

Of course you can't start linnuxcnc without the cards installed.

Chris M
Last edit: 19 Nov 2012 03:06 by cmorley.

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