On Thursday 13 December 2012 20:10:48 andy pugh did opine: > On 13 December 2012 03:39, Gene Heskett <[email protected]> wrote: > > Another thing is (and I don't believe its related to the real problem > > here) that if I slow the pwmgen's prr below about 1350 hz, the > > encoders velocity output gets quite noisy, both in the signal and to > > my ears, its hunting like crazy, but doesn't seem to effect the long > > term average, its just slapping the nominally 5 degrees of play in > > the pulley keyways and timing belt slop. Yet we've been told that a > > lower prr enhances the step level smoothness by making it more base > > thread times wider, where adding a base period to the length is a > > smaller percentage change. > > This is only true as long as the timebase is significantly less than > the time constant of the PWM to Voltage stage. I seem to recall that > you swapped to a much smaller filter cap. > I doubt that the spindle is oscillating at PWM frequency, but perhaps > there is some aliasing effect in play.
For some ultra strange reason, that effect seems to have crawled back into the woodwork, I have it set to 200hz now & its dead stable after todays tuning session. Pgain is considerably lower, so its a bit softer vs load, but thats ok I think, a 5% drop in speed when the bit starts cutting isn't a huge worry. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Marriage is low down, but you spend the rest of your life paying for it. -- Baskins I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
