Ok- so I o-scope'd the mystery wire again this time while taking the table through it's entire length of travel to find that the signal has a few places where it blips high. My question is, if an index signal on these encoders is supposed to give a position reference, why would there be more than one???
Thanks for any info! -Pat On Tue, Nov 10, 2009 at 2:23 PM, pat lyons <[email protected]> wrote: > 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
