John, Sebastian and Peter, Here is a combined reply, using John's post as the basis.
>> What kind of stepper drives? In particular, I'm asking about the inputs. Optocouplers, or non-isolated? Do they have any filtering? << I am using an IM483 micro-stepping driver, the manual can be found here: http://imshome.com/Product%20Manual%20PDF/im483.pdf It has opto-isolated inputs (see page 43) for step, direction and enable, which are the only inputs I am using. The full list of I/O assignments are on pages 12 & 13. >> For the cable, have you tried twisted ribbon cable? Like this: http://media.digikey.com/photos/3M%20Photos/1700^50%20(100SF).jpg << I was not able to find that in pre-made lengths, I could only find flat and rounded so I went with rounded like this (first one): http://www.pc-pitstop.com/scsi_cables/rounded_scsi_cables.asp >> Although that photo seems to show only a few inches of twisted cable between the straight sections, usually it is longer. I have a partial spool that I got surplus a while back, I think it is 18" of twist and then 2" of straight (you have to put the connectors on the straight part). Or maybe it is 16" of twist and 2" of straight, totaling 18" per "segment". I have several cables that are either 3 or 4 segments long that I use in a test computer with a 5i20, and I haven't noticed any noise issues. If you have the IDC connectors, I could send you a 6 foot chunk of cable to try. << Yea, I am familiar with it, I was just trying avoid making my own cables. I don't do it very often, so I invariably have to do it a few times to get a good cable, lined up properly and with good connections on every pin. I appreciate the offer, but I will just order a spool and some connectors, and do it myself if that is what it takes. >> To be honest, I think you are dealing with more than just a cable issue. Flat ribbon cable with grounds on every other pin is really pretty good stuff. And step-dir is not that demanding - we're not talking PCI or even ISA bus, we're talking about pulses that are typically multiple microseconds long. If your signals/grounding are so marginal that 20" of cable clobbers things, you need to look closer - hence my question about the driver inputs. << It is really surprising in that this is the second machine and the first basically worked on the first go. They are both retrofits. The part from stepper drivers through to the motors is unchanged, while everything from the computer up to the stepper drivers has been replaced. I did encounter this at one point on the first system, but it went away when I swapped computers (and possibly cables). I was under a lot of pressure to get that system into production, so I never had the chance to trouble shoot it. However, as I had previously reported to Sebastian, it is working very well. The previous system had some real problems with arcs and generated a lot of jaggies. Under EMC, the jaggies are gone. >From Sebastian: >> Are you sure it's noise in the cable, rather than, say, stepper timings or something? (Every human being should be issued an oscilloscope at birth.) << I have not put a scope on it. My only speculation was that the cable was deforming the stepper square wave enough to cause occasional lost steps. >From Peter: >> Is it possible your STEP and DIR inputs have optocouplers returned to 5V?. This is known problem with the 5I20 (or any of our FPGA cards) outputs since they only swing 0 to 3.3V. << Hmm, maybe a little RTFM time is in order. I wired it up the same as the previous system, which used 5V rather than 3.3. Since the first system worked, I never checked. Thanks, Eric ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
