Steve Blackmore wrote: > On Wed, 19 Aug 2009 22:30:10 -0500, you wrote: > > >> On Wed, Aug 19, 2009 at 10:11:19PM -0500, Jon Elson wrote: >> >> >>> you could put in a one-shot chip to stretch the index pulse >>> >> I said it once already but I don't think everyone caught it: on a >> spindle encoder used for threading and tapping, it doesn't matter >> the slightest bit if you miss the index sometimes. >> > > How many is sometimes? > > >> You certainly must not stretch it longer than one count, whatever >> you do. You would make the cure worse than the problem. >> > > Why - does it read on both rising and falling edge? > > No, it would detect the index true condition whenever it sampled it. There is no edge detection in software, it just samples it until it sees that the bit is true. So, if the sampling is too slow, there will be a jitter that could be as much as one sampling period. At 16 KHz, my guess is that this is not going to cause a huge error in threading at any sane threading RPM. An error of a whole degree probably won't make much of a difference on a typical lathe, this error would be expected to be less than that.
Jon ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
