On Thu, 2007-08-09 at 20:59 -0500, Chris Radek wrote: > On Thu, Aug 09, 2007 at 06:32:45PM -0700, Kirk Wallace wrote: > > What are the major points for choosing a lathe spindle encoder > > resolution? My controller has a count limit of 300k counts per second.
... snip > The quality of the velocity output depends on which encoder counter > you're using. I think the 'encoder' block is currently the best, But doesn't 'encoder' use a digital input such as a parallel port pin, which is way slow? > pluto is adequate (integer number of counts), and ppmc doesn't have > any at all (but I bet you can use ddt). I don't know about > mesa/motenc/etc. > > The problem with using ddt is it will go briefly nuts when the count > resets at an index or wraps around. This is why the driver should > give a velocity output that has these cases handled. For my PPMC, can't I just scale this output to get (angular or RPM) velocity ? -> "• ( S 32) ppmc.<port>.encoder.<channel>.delta – Change in counts since last read." Though, from Jeff's reply, I think I only need to worry about this if I want to have a feed-back loop to control spindle speed. > (On a lathe spindle, though, you won't be relying on index and > velocity at the same time.) > > Hmm, that was fairly rambling. Hope it helps a bit anyway. > > Chris ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
