Eric H. Johnson wrote: > Hi all, > > I am running into a small problem with dropped / excess steps using the > m5i20 board and Hostmot2 driver. The problem appears to be with the 50 pin > cable connecting the m5i20 with the TB. The quick form of my question is, > are there any recommended cables / manufacturers of cables to use with the > Mesa boards in the 18" to 24" range? > > The longer explanation is as follows: > > With the Hostmot2 driver and m5i20 board, the stepper signals come off the > P4 connector, the farthest connector from the point where the cable exits > the computer. One loses about 8" just exiting the computer, so with an 18" > cable, there is only about 10" left to get to the TB. Due to the panel > layout, I really need a 24" cable from this connector. > > I have tried several lengths of ribbon cable, and one rounded cable. The > best performing cable is the 24" rounded (it ought to, it cost about $20). I > need to run about 20 cycles the length of the X axis to lose a quarter turn > of the motor (i.e. drifts towards the min limit). The 18" flat cable will > lose it in about 4 cycles. The stepper motion starts to get rough with a 30" > flat cable, and anything longer (I was testing with a 54" cable) is so > unstable as to basically not work at all. One odd thing is that with the 18" > flat and 24" rounded cables, only the X axis demonstrates this problem, if Y > is having any problem, it is so small that I have so far not been able to > detect it. > > Past the TBs I am using Belden low capacitance cables with individually > twisted pairs, foil shield and drain, plus an overall shield to connect the > stepper signals to the drives. This part appears to be working fine, as > nothing changes if I swap things around past the TBs. > > Any ideas or recommendations? > > Thanks, > Eric
What kind of stepper drives? In particular, I'm asking about the inputs. Optocouplers, or non-isolated? Do they have any filtering? For the cable, have you tried twisted ribbon cable? Like this: http://media.digikey.com/photos/3M%20Photos/1700^50%20(100SF).jpg 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. 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. Regards, John Kasunich ------------------------------------------------------------------------- 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
