On Tuesday 07 November 2017 12:48:24 Nicklas Karlsson wrote: > On Tue, 7 Nov 2017 12:28:31 -0500 > > Gene Heskett <[email protected]> wrote: > > On Tuesday 07 November 2017 10:08:33 Peter C. Wallace wrote: > > > On Tue, 7 Nov 2017, Gene Heskett wrote: > > > > I fail to see why a 2 or 3 percent error in duty cycle and or > > > > quadrature results in so much noise. There simply is no way in > > > > hell that spindle can be moving at 200 rpms on one servo-thread > > > > sample, and 600 rpms on the next sample one millisecond later > > > > while its filtered display on a pyvcp tach dial says 400 rpms. > > Mean value = (200rpms + 600rpms)/2 = 800rpms/2 = 400 rpms. > > 2 pulses each millisecond, add some noise and sometimes it is 1 pulse > while other times 3 pulses each millisecond. Multiply by 200 => 200*(1 > 2 3) = (200, 400, 600). > > How many pulses each time value is calculated? > Obviously not enough. At 300 revs, thats 300/60 to get 5 rps. Divide that by 264 gets the milliseconds between encoder passing edges=0.078125 seconds between velocity updates read at a KHz servo rate. So at 300 rpms, its 78 milliseconds before a new velocity is available. So the same value is fed to lcnc 78 times before a new value becomes available.
Right? Or did I screw the moose pushing calculator buttons? Must have, 5 rps is 264*5=1320 edges a second, and the reciprocal of that is 0.000757575757575757576, which is faster that lcnc's read rate, just enough to drive it berzerkers. Sure a 5000 line encoder would theoretically help, but what printer could I steal THAT out of... Rhetorical Q, the choice here is limited to an epson nx515, whose printer plugged its nozzles 2 weeks after I bought it years ago, but I kept around because the scanner in its top worked yet if you stuck a brick under the front edge because some marketing "genius" thought it would be sexy if it was tilted forward so far that you need to glue the paper to the glass to keep it from sliding out while closing the platen lid. Today its surplus as I now have an 11x17 brother printer/scanner. Thanks Nicklas. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
