On Saturday, 16 April 2022 13:17:16 EDT Torsten Curdt via Emc-developers wrote: > > > But this feedback loop decouples the real position from the > > > meant-to-be position. (expressed in the following error) > > > And I don't see how the real position could be reported back to > > > LinuxCNC> > > so > > > > > it's still in full control of the movement. > > > ...unless you connect the encoder directly to the Mesa instead of > > > the > > > Closed Loop Stepper driver. > > > > You can send the encoder feedback to lcnc as well as the drive using > > splitter. > > Ah, interesting. > > The encoders on closed loop steppers seem to usually have 4 pins. > (EA+,EB+,EB-,EA-)
For noise considerations, the Lichuan motors and drivers (LCDA357H) are differential. > Does that mean it requires 4 inputs per motor? Or would this somehow be > normalized into STEPs and DIRs? Or what does LinuxCNC expect? The encoders are quadrature, so the diff is low, but the splitter could easily turn that signal pair into a TTL level signal. In fact, and not for a 3 phase setup, I'm doing that conversion mid-cable on my Go704. Using $2.50 rs485 interfaces solder programmed for 1 way only signaling. > The splitting would not work for the servos that have the driver > integrated though. Why not? > For example JMC Servos can only provide feedback via modbus for > example. So I guess they wouldn't be really ideal to work with unless > LinuxCNC could also poll the modbus as a feedback channel. > > It sounds like the ideal LinuxCNC setup would be a very dump driver > (without encoder support) and a stepper/servo with just an exposed > encoder. And then have LinuxCNC take care of everything. > Does that sound about right? See wiki.linuxcnc.org, its been done around a decade ago. Nyquist related phase errors I believe limited the speed, but might work better feeding mesa stepgens and encoders since they're much faster than software. > cheers, > Torsten Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
