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PCW,
Nice board. 
I lack some fundamental electrical knowledge. In general, on a line driver type differential encoder, if the receiver is only single ended (my drive), it was my understanding that one can still read in just the A and B channels. If so, do /A and /B need further termination or can they be left floating/unconnected? 
Or is it better to just get a single ended encoder if the receiver is single ended? 

Tommylight,
I have a split setup on a lathe spindle that works very well with rigid tapping / threading and css. I'm reading in differential on both ends one to encoder card on vfd and the other to 7i77 for velocity control, so not trying something odd like current setup.

Current problem is trying to get a 4th axis indexer working. The drive (AMC ab30a200) only reads in single ended encoder for velocity feedback. I'm not sure why a new analog drive would have limited encoder channels in addition there is no encoder out from the drive to linuxcnc.
I think most of the digital drives have the additional encoder output. Unless I'm missing something, I'm forced to split it if I want encoder feedback.
One option is I can use current mode in the drive and read in the encoder on 7i77 only. Unfortunately  I can't get good shaft lock in current mode.
Best option so far is hall velocity feedback in the drive and encoder to 7i77. Shaft lock is good but runs somewhat rough. Suspecting noise and bad encoder signals. This drive is not isolated. That was an extra option.



 

How can I use GPIO digital output to handle motor direction?
Like PCW said, it could've been simpler with negative and positive analog voltages for both speed and directions but Like I said earlier, I imagined the drive analog output of 7i77 as external pot controlling the BLDC. I tried and it works. The motor spins with the analog out from 7i77 in open loop test in pncconf.

how to set gpio pin to control forward/reverse function for this application. Axis motor direction seems critical so is using signals on servo thread might not be a good idea. What other option do I have?

@ besriworld Again configured as spindle, I need to set F/R somehow.

Hoestly I am confused too.

 

This is what is mentioned on my drive. Made me think that Pulse input is meant step/dir digital signals and PWM meant analog!!

 

I don't know what difference the modes are on the drive. The dip switches modes that are in the first picture are printed on the drives too. Are the modes mentioned different or the same?

@Tommylight said  it is analog and so I thought that. Anyways, Help me with this.6i25 p3 to 7i76, p2 to 7i74, sserial link between 7i76 and 7i74. Which port on 7i74 is sserial (default is port 8 I guess). 3 axes, one spindle and spindle encoder to 7i76, 3 linear scales on the axes to 7i74 making it closed loop. Would this work?

Found it, I thought I had commented out the invert line in my hal, I had not:

# --- SPINDLE-ENABLE ---
net spindle-enable => hm2_7i92.0.7i76.0.3.output-05
setp hm2_7i92.0.7i76.0.3.output-05-invert true

Do you mean 7I77 analog enable?

If so, this is a switch, not a voltage source
so you would need to wire:

+24V --> 7I77 ENA5+
7I77 ENA5- --> SPINDLE ENABLE IN

Finally got my encoders in, MDI S2000m3 and I get no response. Probing the analog 5 output, I see voltage (3.3v approx), which is what is expected. Probing my spindle enable output (7i76 Output 5), I see 0v. Checkng hal config, the LED is "on" for the 7i76 Output 5. If I apply 24v directly to this output pin I get spindle activity. I do not have a spindle encoder hooked up yet.

Thanks for the response, sorry for the late reply.

That configuration sounds good but after using the config tool linked above I am slightly favoring the 7i77 + 7i96S for the additional IO/less cards/similar price. Is there any reason that's a bad idea?

another question I have after reviewing the 7i96S Documentation is about the analogue spindle interface. my spindle controller is expecting to see a voltage between 0-10v for the speed reference, the 96s Docs say "The voltage supplied between SPINDLE+ and SPINDLE- must be between 5 VDC an 20 VDC" this is referring to the voltage between spindle- and spindle+ ( ie 0 to 10 is a change of 10 and so fine) NOT the voltages that spindle- and + must fall between (ie spindle- being 6 and + being 15) right? In other words 0-10v for spindle-+ should be no problem right?

Thanks

Exactly. I've printed it already..

That's a huge step for me, thanks for your patience.

So I guess, that I need to go back to mesact, call up the 7i77 again, enter as much machine info as I can for all axes and the spindle, and from then on I am away from that GUI and into text.

LinuxCNC can do up to 9 axis, so yes you can do a single axis CNC (which is what an ELS is). I did that on my Boley, for which I had no change gears. I just made up a bracket to mount a motor and pulleys to drive the lead screw, kludged up an encoder, and PSU, and used a PC to control it. Was never a permanent solution, I only used it to cut the nose spindle thread in a backing plate.

Backlash is less of an issue for a lathe than a mill, as you mostly don't change direction with the tool in the part (at least not on both axis), and you don't have the issue of climb milling. My mini lathe has pretty bad backlash on both axis, but can still turn somewhat precise parts open loop using LinuxCNC's backlash compensation.  I suspect that closed loop with linear encoders, with significant backlash in the screws, would be pretty tricky to tune the PID loops on.
However, as Cornholio said, it is best to simply engineer out the backlash. The Schaublin has no linear encoders, so I am DROing off the motor encoders. I would not buy a ballscrew kit with cheap rolled screws. Get some nice C3 or better ground ballscrews pulled from a fab in Korea, and make up you own mounts.

One of the big advantages of CNC is that you can put on enclosure, or at least better shielding around the chuck and constrain the mess.
You mentioned using an ELS to cut to a shoulder. Nicer is using two axis CNC, to cut to the shoulder, then retract out before it starts rubbing and chattering, and returning for multiple passes
However I also really like manual lathes for quick bodge jobs which need no precision, and like the "feel" of machining on a manual lathe.

As Cornholio has said, if you are going to end up with a full CNC, you are probably better off doing it all in one go. Doing a mixed CNC/manual interface is harder to do well, than one or the other.
With the Schaublin, I found my initial use of the machine, with a loose wireless keyboard, and touch monitor leaning aginst the tailstock, to be pretty sketchy and unsafe.  I felt a lot more comfortable with the safety once I built the control module with some physical buttons like feed hold, the encoder for feedoverride, and the jogging joystick etc.

The 7i73 is so cheap, having a single Cat 5 cable to you human interface can saves hour of discrete wiring.

I choose that set of diverse cards on the Schaublin for two reasons:
1/ when I went through and made a list of all the I/O, encoders, etc it would need, it was not going to work on one of the integrated cards. I currently have six encoders, (Spindle, X motor, Z motor, feed override, spindle override, jog override), with two more planned ( X Jog wheel, and Z jog wheel on a manual jog pendant). I also need a second 7i84, instead of the sketchy relay board to use available 7i84 5V outputs to switch 24V loads.
2/ I knew I would have a space challenge, and breaking up the cards reduced the need for a single big footprint in the control cabinet.

On the mini lathe, I just used a 7i96, and on the Maho a 5i25/7i77 (The 7i97 didn't exist yet), plus a 7i84 as it needed addition I/O.
Cheers,
Mark
 

Thanks for all the help - I'm 1 failed encoder away from being able to use MDI to test the spindle. I may try that simple HAL file if I get time.

Also  I'm not sure if pncconf's open loop test can really access much other than
the axis analog outputs. A better test might be a very minimal hal file:

loadrt hostmot2
loadrt hm2_eth board_ip=10.10.10.10
loadrt threads
addf hm2_7i92.0.read thread1
addf hm2_7i92.0.write thread1
start
loadusr halshow

And then run this file with:

halcmd -f testfile.hal

or just

halcmd -kf

 and enter the lines by hand or copy-paste

At this point you should be able to set and view pins
with halshow

When done you will need to run:

halrun -U

To unload the drivers.




 

Maybe this helps
forum.linuxcnc.org/10-advanced-configura...ning-detailed-how-to

Right now I can't get to MDI as the encoders are giving me fits, I can only move in "Open Loop" test mode in PNCConf. Once I get my encoders sorted, I'll try this, but right now I have zero response in PNCConf.

I would set the spindle speed to 1/2 full scale (3000)

(MDI)
M3S3000

and see if these make sense

hm2_7i92.0.7i77.0.1.analogout5
hm2_7i92.0.7i77.0.1.spinena

Then check the analog 5 output

So I'm in PNCConf and I have my linear motors moving in open loop test mode, but when I go to open loop test mode on the Spindle tab, I get no DC Voltage output on the 7i77 Analog output 5.  HAL shows an output, but the multimeter shows nothing.  Attached are my 2 hal files and my ini.  Also is there a way to have a different max linear speed for my Z axis?  The head is heavy and the motor is tired, doesn't want to move it at 300ipm, but the x and y have no problem.