> > When going through my testing for this the first time I cranked all 4 > > settings up to 10,000 - the problem still occurred. After I tried > > inverting the output I slowly stepped them back down - for my G540 I > > settled on 700/700/2000/2000.
> The Gecko 540 is not in the charts of our wiki, darnit. What is there isn't even that fast. See: Yeah, I've thought about adding it a couple of times - but would want to do some more... intense testing before adding my timings there. > <http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Stepper_Drive_Timing> > I take it you do not have any opto-isolation in those 3 paths. That 700 ns is pushing an opto's ability to switch that fast. The BoB I used was all opto, and I was warned about its speed by someone (Steve Stallings?) on this > list. I don't recall which channel now, but I had to remove one of them and jumper across it. I think there are probably faster opto's about, but what I saw on the scope just wasn't up to getting the job done. All the loads that > BoB see's are already isolated, so I wasn't terribly concerned about losing one stage of isolation. I have no additional opto-isolation in that path - I believe that the G540 uses fast opto's on all the parallel port pins (from the manual, I'm sure there was a post on cnczone detailed the choice of isolater somewhere) To clarify, the figures I gave were in the format DIRSETUP/DIRHOLD/STEPLEN/STEPSPACE. Gecko give their recommendations on timings for the drive here: http://www.geckodrive.com/geckodrive-step-motor-drives/g540.html Those indicate 2000 nS for '0' on-time, 1000 nS for '1' on-time, 200 nS for direction setup and hold. So it looks like I'm just within their recommendations on step length. I'm hooked up to a 5i25 instead of a parport though. > All my drivers are just 3 types, 2M542's, 2m860 and Pico pwm-servo's for > 2 of the 3 spindles at my place. And I'm not pushing any of them that fast. But because of that slow BoB, ISTR I am running dir setup and dir hold about 1.5x longer than the wiki shows for the LeadShines. So my experience is not > with a wide range of drivers, but I will no longer consider opto-isolated BoB's because everything I have is already isolated. Best BoB IMO, 10ns response times, but its been taken down, is the cnc4pc C1G that I have 2 of. What he > is selling now is NOT the versions I have. Everything on mine has an led tally, which simplifies troubleshooting considerably. > Also, generally, where you have the choice of commonizing the + terminal of a driver loads input, you are far better off doing that, and having the BoB pull it to ground as the pulldown in most TTL circuits is much more robust. > Having the reverse setup, where the - terminals are commonized, is generally NOT a good idea due to a lesser amount of pullup power to light up the opto in the drivers own input. I've gone to using mesa cards for pretty much all my interface as far as possible, I've had odd issues with Gecko and Leadshine drives, I've managed to work around them so far. The industrial drives I have used have generally behaved better. Since the machines I'm converting seem to be getting larger, I thankfully get to use servos more than steppers these days. The one I haven't tried yet, but would be curious to see if anyone has comments on is the Argon or Ion from Granite Devices. Ben ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
