On Sunday 05 April 2020 01:29:50 andrew beck wrote: > Hey guys. Just getting back to this while we all have some free time. > > Todd could you please confirm what card you use for closing the loop > back to the control when using step and direction control? I want the > most encoders and general io I can get Ideally. Don't need serial > ports etc..
Depending on the firmware you put in it, the 7i90 can have 4 to 8 stepgens, and 4 pwm-gens, and 4 encoders. You can talk to it over spi, or you could use a 5i25. And it has a 3rd 16 bit wide and faster means if the parport is totally bi-dir. All its i/o, 72 pins worth, is a bit fragile, just barely tolerant of 5 volts and to be safe around a box full of stepper drivers, needs 3 7i42TA's for protection, but that also makes hookup a piece of cake by giving you the usual green screw terminals to wire it up. That is what I'm using to drive an 11x54 sheldon from a pi4, and I've still enough i/o left over to handle a 6 pole turret mount. > On Thu, Feb 13, 2020, 3:13 AM Todd Zuercher <to...@pgrahamdunn.com> wrote: > > 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. I've 2 of the mpja encoder dials, 100ppr style on the sheldons new front apron so I can drive it by hand. Rigged up in hal for jog sizes from .0001" to .020" per click on a 1-2-5 scale, which is fast enough to hit either axises speed limits. But all that runs in a 200hz thread, not in the servo thread. And I've still got gpio's, 30 or so that I haven't used. And if I survive the virus, thinking of converting the step/dir steppers to step/dir controlled 3 phase servo's. > > 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. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
