SSI absolute encoders and analog servos

Hi,

We are going to replace control on our old Cincinnati HMC. Machine has analog servos(+-10V) and SSI linear encoders(servos do not have internal encoders at all only tachos). My question is what Mesa boards I need for reading 4 SSI encoders and controlling 4 analog servos? Machine also has about 100 digital inputs and outputs for ATC and other on/off functions.

Tero

Any FPGA card will work, for the SSI encoders you want a daughtercard with at least 4 RS-422 channels
perhaps a 5I25/6I25/7I92/7I80DB and 1 or 2 7I74s
The SSI encoders will connect to 4 of the the 7I74 RS-422 interfaces
a 7I83 (6 analog out) connects to 1 RS-422 interface leaving 3 RS-422 interfaces for digital I/O cards
3 I/O digital I/O cards could give you 96 inputs and 48 outputs for example (2x 7I70 and 1x 7I71)
or 128 inputs and 16 outputs (2x 7I70 and 1x 7I84)

Hi,

I have now selected:

6I25 1 pcs
7I74 1 pcs
7I83 1 pcs
7I70 2 pcs
7I71 1 pcs

These cards are all compatible with LinuxCNC? And should be a working combination? Also if I want to think about future and upgrading analog servo drives to digital at some point, can I install 7178 daughter card to another port of 5i25?


Tero

terkaa wrote: I have now selected:
6I25 1 pcs
7I74 1 pcs
7I83 1 pcs
7I70 2 pcs
7I71 1 pcs
These cards are all compatible with LinuxCNC? And should be a working combination?

Yes, that should be a working combination. You will need to flash the 6i25 with a suitable bitfile and I can't see a mixed SSI / Smart-Serial bitfile in the LinuxCNC firmware repository or the 5i25 set downloadable from Mesa. However you can either get PCW to make one, one of us might be able to do it, or you can download the Xylinx webkit and so it yourself.

Hmmm smart-serial? PCW intrested in making one? I am afraid this goes beyond my skills.



Tero

Hi,

I have been looking into this. And another option for reading position would be with modbus from servo drive(motors have multiturn absolute encoders and position is true absolute). Also it would be possible to drive motors through modbus. Would this be possible with LinuxCNC? Has someone done this in the past?

Tero

There is not (as far as I know) a real-time Modbus interface to LinuxCNC HAL.

And encoder feedback is one place where you really want realtime.

Hi,

Ok so I will stick with original plan. Is there a bit file for 5i25 + 7i74 + 7i83 combo? I installed LinuxCNC on this laptop and downloaded 5i25 firmware files from Mesanet. But I cant see how to make this kind of configuration. Also selecting config with 7i74 gives me following error:

PNCconf encountered an error. The following information may be useful in troubleshooting:

Traceback (most recent call last):
File "/usr/bin/pncconf", line 2891, in on_mesa_component_value_changed
self.set_mesa_options(boardnum,title,firmware,numofpwmgens,numoftppwmgens,numofstepgens,numofencoders,numofsserialports,numofsserialchannels)
File "/usr/bin/pncconf", line 2999, in set_mesa_options
numofpwmgens,numoftppwmgens,numofstepgens,None,numofsserialports,numofsserialchannels,False)
File "/usr/bin/pncconf", line 3356, in firmware_to_widgets
self.widgets[p].set_model(self.d)
File "/usr/bin/pncconf", line 1127, in __getitem__
return getattr(self, item)
AttributeError: Data instance has no attribute '_sserial6_signalfilter'

If you post that last message to the Pncconf section hopefully Chris will see it.

freeby.mesanet.com/ssi_ss.zip
Has bit and added source files for a 5i25/6i25 8xSSI+8xSSerial config for a 1 or 2 7I74s
(4 SSI+4SSerial per 7I74 SSI channels first on 7I74 (0..3), SSerial last (4..7))