The machine I am using this on was already set up and running Linuxcnc, but only using software stepping (but not using a parallel port for the I/O). I was having a lot of trouble getting a good tune on the servos as well. At that time the 7i85S, was the only option for hardware step generation and encoder feedback. And since the machine was already set up and running Linuxcnc I didn't need to worry about hooking up other gpio. Unfortunately once the existing PC dies, I will probably have to buy something else for the gpio, because it is using a rather expensive ISA card for that. Not to mention the fact that I can't seem to get a real time os newer than our old Ubuntu 10.04 .ISO to run on that ISA/PCI slot motherboard. I'll probably just end up buying a 7i84 and scrap all of the old IO boards that go with that old ISA card, when that day comes.
The 7i76 only has one encoder input and the 7i76e or any of the other Ethernet cards didn't exist yet (at that time). The 7i84 is a Smart Serial card and is only serviced at servo thread speeds, so it's only good for gpio with no encoder inputs (the two MPG inputs don't count because they aren't fast enough for servo use). I think the 7i84 is pretty much exactly the same as the built in GPIO on the 7i76. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: andrew beck <andrewbeck0...@gmail.com> Sent: Tuesday, February 11, 2020 7:30 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] closing the loop in linuxcnc with a 7i76 mesa card and step direction control [EXTERNAL EMAIL] Be sure links are safe. Hey Todd. Was there a reason you went to a 7i85 rather than a 7i76 and 7i84? All I can think of is you didn't need the extra io of the 7i76. So could do it with only two cards. Regards Andrew On Wed, Feb 12, 2020, 3:11 AM Todd Zuercher <to...@pgrahamdunn.com> wrote: > I'm using a 5i25+7i85s to run a large gang router with step/dir servos. > This machine has a lot of mechanical warts that have made getting a > good tune on the servos difficult. Having the encoder feedback made > tuning a little easier, and saves me from having to break out the > o-scope to work on it. > > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > -----Original Message----- > From: andrew beck <andrewbeck0...@gmail.com> > Sent: Monday, February 10, 2020 7:11 PM > To: Enhanced Machine Controller (EMC) > <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] closing the loop in linuxcnc with a 7i76 mesa > card and step direction control > > [EXTERNAL EMAIL] Be sure links are safe. > > Awesome Todd > > What Mesa card did you use? And do you mind if I pick your brains on > this rather than reinventing the wheel. I would love to see a config > that works so I can compare it with what I have and make the needed changes. > > Also did you find the motion was uneven or did it just work as expected. > > Regards > > Andrew > > On Tue, Feb 11, 2020, 11:20 AM Todd Zuercher <to...@pgrahamdunn.com> > wrote: > > > It works very much similar to running them with an analog input. > > The encoder feedback can also be handy for double checking the > > tuning of your servo drives. > > > > You simply disconnect the position feedback from the stepgen and use > > the feedback from the encoders to connect to the PID and the joint > position-fb. > > > > You will need to tune the feedback loop, P=1000 will no longer be > > valid, and will likely have to be significantly less (guess 1/2-2/3) > > > > Todd Zuercher > > P. Graham Dunn Inc. > > 630 Henry Street > > Dalton, Ohio 44618 > > Phone: (330)828-2105ext. 2031 > > > > -----Original Message----- > > From: andrew beck <andrewbeck0...@gmail.com> > > Sent: Monday, February 10, 2020 4:46 PM > > To: Enhanced Machine Controller (EMC) > > <emc-users@lists.sourceforge.net> > > Subject: Re: [Emc-users] closing the loop in linuxcnc with a 7i76 > > mesa card and step direction control > > > > [EXTERNAL EMAIL] Be sure links are safe. > > > > Actually all I want to do is be able to home to index. Which I > > might be able to do now. As my servo can output a encoder Z pulse. > > > > And I want to have linuxcnc remember where it is if I disable the servos. > > That is now a massive deal but I get a bit sick of continously > > homing the machine every time I push the E stop in and disable power > > to servos. It would be nice to have the encoders still counting > > once the servos are disabled. ( drives would still be on just not > > running a PID > > loop.) > > > > And yes I was wondering what trying to run a PID loop on a position > > servo loop causes. > > > > Regards > > > > Andrew > > > > > > > > On Tue, Feb 11, 2020, 2:14 AM andy pugh <bodge...@gmail.com> wrote: > > > > > On Mon, 10 Feb 2020 at 10:30, andrew beck > > > <andrewbeck0...@gmail.com> > > > wrote: > > > > On the back burner though I want to > > > "close the loop" back into linuxcnc with a 7i84 mesa card I think. > > > Has anyone done that before with a step direction control system? > > > > > > What do you anticipate gaining from bringing the encoders back to > > LinuxCNC? > > > > > > If this is a stepper system (it's not clear without inbox-mining) > > > then a PID will naturally attempt to run the motors faster, with > > > the reverse of the hoped-for result. > > > It is probably possible to simultaneously reduce the feed rate > > > with adaptve feed and then attempt to recover the lost steps, but > > > I don't know if anyone has tried that. > > > > > > If it is a step-servo system then the drives will already be doing > > > all that they can. You won't gain much from bringing the motor > > > encoder data in to LinuxCNC. > > > However, you might be able to gain accuracy by adding linear > > > scales to the system, and using the feedback from them to modify > > > the motor position commands. > > > > > > -- > > > atp > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > designed for the especial use of mechanical geniuses, daredevils > > > and > > lunatics." > > > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
