On Wed, 12 Oct 2016, Marius Alksnys wrote: > Date: Wed, 12 Oct 2016 14:59:54 +0300 > From: Marius Alksnys <mar...@robotise.lt> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Homing to index ends at different positions > > Thank you for your suggestions, Peter. > In this case Z assembly weights probably several hundred kilograms. And > I don't have a big wish to remove the servo motor, although possible. > Releasing the electromechanical brake makes it drop really fast. > > By the way, I have never succeeded "setsing" or "setping" an encoder > index-enable signal and waiting for it to go down by rotating the > encoder by hand on other setups. I don't remember the exact behavior > now. I thought it has something to do with less often used IO type of > HAL pin.. But a bit of time passed, I should check that again. > If the latch move is slow enough (so the index signal is capturable by halscope with a servo thread update rate), capturing a halscope trace of index and index-enable might help diagnosis
setp-ing the index-enable pin will not work, but sets-ing the signal that carries the index-enable does work and does not require disconnecting hal pins > What is interesting, while not proven, that encoder count (or rawcount) > persists between different LinuxCNC sessions and resets only after 7i77 > 5V power is re-applied. And exactly then I observe different Z position > after homing. > These things are not easy to prove, as they require big number of > different tries. The 7I77 cannot "store" any encoder counts as it only has encoder input signal conditioning on card, though cycling the 7I77 power when LinuxCNC is running will like cause a few stray counts. Note the raw counts are not cleared at linuxcnc start so can be any initial value (encoder counts and position _are_ cleared at linuxcnc startup and encoder position is cleared by index if index enable is true). Is it possible that something on the drive changes with 7I77 power cycles. > > >> I would hand check index detection by "setsing" the appropriate index-enable >> signal and turning the axis by hand and watching for the same index-enable >> signal to be cleared. If this does not work reliably it suggests you have a >> encoder index signal interface problem of some sort (wrong interface mode, >> too short index signal, missing index from resolver-digital converter, 5V >> problem on 7I77, cable issues etc) >> >> The encoder errors also suggest some kind of generic interface issue >> >> Another diagnostic would be to halscope the index pulse itself assuming you >> can move slowly enough to detect it in the servo thread, index pulses are >> often 1 encoder pitch wide (1/2048 in your case) so you would have to move >> more slowly than 2s seconds per turn to reliably detect it at a 1 KHz servo >> thread >> >> >> >> Peter Wallace >> Mesa Electronics >> >> >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, SlashDot.org! http://sdm.link/slashdot >> > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
