In addition to what Peter said, it is unlikely that adding encoder feedback to Linuxcnc will improve their accuracy or error tolerance. Most decent quality servo drives do as good or better with encoder error detection than Linuxcnc. So if their servo drive is missing or picking up false encoder counts more than likely Linuxcnc will do the same. There are always possible exceptions to that, a good example might be an old Gecko 320 servo drive. Another possibility is if the step/dir commands are not being received properly due to noise or another electrical problem, this situation probably would improve when closing the position loop in Linuxcnc (provided the encoder signals are clean.)
That said for diagnostic purposes it might be advantageous to connect the feedback from each axis temporarily in turn to the 7i76E's single encoder feedback for testing purposes, and to check the signal quality. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Peter Wallace <p...@mesanet.com> Sent: Monday, September 25, 2023 12:05 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] 3 encoders on 7i76E? [EXTERNAL EMAIL] Be sure links are safe. On Mon, 25 Sep 2023, Viesturs L?cis wrote: > Date: Mon, 25 Sep 2023 18:47:03 +0300 > From: "[UTF-8] Viesturs L?cis" <viesturs.la...@gmail.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > Subject: [Emc-users] 3 encoders on 7i76E? > > Hello! > > I am trying to help a guy to sort out config changes for their LinuxCNC > machine. > Currently they are running servo motors with step/dir signals and > there is no position feedback to LinuxCNC. They are having some issues > with machining errors and they want to change the config so that > encoder signal from servodrive is fed to LinuxCNC with an intention > that it will improve positioning precision. 7i76E is supposed to be > capable of reading 3 encoders - one for spindle and two for MPG. The > idea is to use these 3 encoders for X and Y axes (it is a gantry > machine with total of 3 joints for XY plane). > > The problem is that this line in INI file: > CONFIG="num_encoders=3 num_stepgens=4 sserial_port_0=0xxxxxxx" > > Gives an error on LinuxCNC startup and I believe this line to be the crucial: > config.num_encoders = 3, but only 1 are available, not loading the > driver The num-encoders line only applies to quadrature encoders built into the FPGA (and there is only 1 quadrature encoder in the standard 7I76E firmware) If you wish to use the MPG encoders, you must use sserial mode 2: ( sserial_port_0=2xxxxxxx ) and the 7i76 mpg encoder hal pins > > Do I understand correctly that simple change of firmware is required? > Can someone suggest what would be correct firmware for this? > This is standard > And then one more question - are those inputs for MPG encoders > suitable to read "normal" encoder signal, meaning - are there any > limitations on max pulse frequency the inputs can handle for these 2 > encoders? > They are quite limited (to say 40,000 counts per second) In addition they are single ended only and do not support index In general they are not recommended for motion applications and rather just for supporting MPGs A much better solution is to add a 7I85 or 7I85S > Thanks in advance! > > Viesturs > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://list/ > s.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=05%7C01%7Ctoddz% > 40pgrahamdunn.com%7Ca221c8a563624364bf3c08dbbde14d64%7C5758544c573f47c > ebee96c3e0806fb43%7C0%7C0%7C638312547604979777%7CUnknown%7CTWFpbGZsb3d > 8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C > 3000%7C%7C%7C&sdata=w0Fr4Dlp9vKXUc04CtmJaOHxsUZZj9NbSZx%2BWzJPfec%3D&r > eserved=0 > Peter Wallace Mesa Electronics _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
