On Friday 20 March 2020 23:48:46 Leonardo Marsaglia wrote: > Hello guys, > > I'm testing a phisical encoder to simulate how the spindle will work > with the external offsets. So far so good but I need to clarify > something that I suspect. Here it comes: > > The encoder I'm testing is an ERN471 from Heidenhain. A beast of > encoder. It says 5.000 line counts on the datasheet but also says it > outputs 125.000 signal periods per revolution, so when I read it in > LinuxCNC with a scale of 1 I find that I'm having 500.000 pulses per > turn. A lot of resolution.
Yes, too much, there little to be gained by going smaller than 1 degree. A $20 OMRON ball bearing model from ebay with 1000 lines per rev is more that enough. Save that for motorizing an HS-1 to put gear cutting in the lights out category. > I'm scaling it to 1024 since this is what I > have on the Mazak. You should set the SCALE in the ini file for whatever counts it hits in one revolution. I have code that measures that for 100 triggers of the index, and I divide that count by 100 to set the ini files SCALE. I also have tally switches on the head gearshifter to change the scale multiplier so the tach remains dead accurate. > My concern is (and I think this is to be expected) that I have missing > index pulses if I rotate the encoder too fast with my fingers. I tried > to use a shorter servo-period and that seemed to improve things a > little but not solving the problem always. > > Is this what's happening? Should I not expect this behaviour with the > 1024 PPR encoder and the spindle turning at about 200 RPM ? > > I would like to hear your thoughts just to be relaxed, since a missing > index pulse on this kind of processes is likely to break the tool and > spoil the part. > > Thanks as always! I think I'd put a 1 shot chip in the index line to stretch the index pulse several times, sending a lengthened pulse to the encoder's index.input. Do it ship in a pill bottle style with the trimpot mounted you can trim it while you can look at the pulse hitting the index.input and adjust the trimpot so as to make sure the 1 shot recovers within 1/2 a rev with the spindle at its maximum rpm. > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
