Andy Pugh wrote: > 2009/10/2 Steve Blackmore <st...@pilotltd.net>: > > >> On page 6 I changed the sampling rate to base thread. >> >> http://filebin.ca/wacbfm/screenshots.pdf >> > > Aha! I see noisy encoder signals. That seems to be confusing the > velocity calculation (but possibly not the position calculation) > I am also a little surprised that the mark-space ratio on channels A > and B differs. I don't know enough about the subject to know if that > matters. > OOOHHHH! I think you have something! YES, this actually makes sense! The velocity calculation uses the time of the last edge coming in to compute velocity. If you have noise on the encoder signals (A & B), then the time of the last edge may not be relevant to the last valid count, or if the encoder is just "dithering" it will show much higher velocity than would be measured by position delta.
Does the velocity calc require a valid quadrature transtiion, or does it count ANY transition on the A and B inputs? Also, if the encoder is dithering rapidly while not moving at all beyond the +/- 1 count, does that count as a high velocity? I think it has to, the way the code is written. There was a chip that did the quadrature to analog tach conversion, it had two frequency to voltage converters, that were differentially summed. One for each direction. So, encoder dithering would cancel out by summing. Jon ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
