Guys thanks a TON for the suggestions and info, I will be looking into them and I'll letcha know what the outcome is!
-pat Sent from my iPhone On Nov 10, 2009, at 2:06 PM, Gene Heskett <[email protected]> wrote: > On Tuesday 10 November 2009, Pat Lyons wrote: >> my photo attachment of the red slide unit was rejected cause it was >> too big >> a file. >> >> I have a new question though- >> >> is it possible that these encoders can be counted on both the >> rising and >> falling edge of both signals? >> in other words: >> >> if I count the falling edges on one wire as *640 falling edges per >> inch*, >> does this actually mean its *640 x 2* for rising and falling edges? >> then x2 >> again for two signal quadrature? or is the quadrature pair only to >> provide >> direction information? >> >> thanks! >> -pat > > Pat: There are logic diagrams extant here on the web, check the > major chip > makers sites for application notes (and the wiki.linuxcnc.org pages > too) and > even complete chips available today that can derive from those > quadrature > outputs, a complete, valid # of steps and instant direction from > them. The > only use for the index pulse is so that the count can be zeroed at a > specific > point in the rotation. And in order for this to not have a > potential of a > one or two count ambiguity is if the index pulse is narrower than a > single > edge count going either way, eg the index must be narrow enough, and > well > centered in the time frame where both A&B are high or both A&B are > low. > Either that, which requires some decent precision in making the > encoder, or a > method worked out in the logic so that it will only use one edge of > the index > pulse, and which edge corresponds to the instant state of the > direction > signal. I haven't worked out that bit of logic but I believe it > could be > done. And it would certainly present the least restrictions on how > sloppily > the encoder is made. > > Thinking about the index 'problem', it might be possible to use the > index > pulse edge detected by the correct edge via using the instant > direction state > to select which edge of the index was actually the correct one. > > Here are 2 chips that might be usable: > <http://www.avagotech.com/docs/AV02-0096EN> > > And also Pico Systems (our own Jon Elson) makes a board that can > apparently > handle 4 encoders, but I wasn't able to make the web page show me > much about > it. It does 24 bit counting. > > Other choices are just a google away. > > -- > 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) > The NRA is offering FREE Associate memberships to anyone who wants > them. > <https://www.nrahq.org/nrabonus/accept-membership.asp> > > We will have solar energy as soon as the utility companies solve one > technical > problem -- how to run a sunbeam through a meter. > > --- > --- > --- > --------------------------------------------------------------------- > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
