Steppers and servos

Please excuse me if this has been discussed before, and point me to the appropriate thread or instructions.

I purchased a 5i20, 7i33, (2x)7i37 package for a kneemill with a rotary axis. This gives me the four needed servo axis' and plenty of I/O.

Now I need a step/dir output, probably from the D510MO parallel port, to raise and lower the knee. This is only for positioning, not coordinated motion. I intend to use the knee for tool length compensation as the quill only gives me 5 inches of travel.

My question concerns the practicality of using the parallel port in S/D mode while also having 4 axis servo control thru the Mesa cards. Is this advisable, easy, doable within pncconf?

Thanks;
Doug

Doug,
the 5i20 has 72 pins available , and is a pci card direct to the pc buss , so you dont need to use the parrallel port , use 2 of the general purpose io pins available
you may need to customise the firmware for the 5I20 to obtain the required uses , but that should not be too much of a problem .

shout if you need a customised BIT file to suit , your requirements .
i'd need a list of how many servo , stepgens , pwm gen , io pins etc , to produce one
at trhe moment i dont have a 5I20 to test with , so it would be compiled and up to you to test etc

firmware SVST4_8 has 8 PWM, 8 encoders, and 4 step gens (maximum)

Not sure if rooting step pulses through the 7i37 works well (timing wise) - maybe Peter will chime in.

Anyways to answer your original question. Yes you could have software stepping thru the parallel port with servo controls thru Mesa's board.
but there is probably better combinations ( as noted).
PNCconf will not build configs that include software stepping and assuming you would like the knee as W it won't help there either.
But it cans build the servo XYZA machine (get that running happily) and then you can hand edit in either a software or hardware stepping knee control.
You could build a hardware stepper base dummy config with PNCconf and copy one axis over, changing it to W axis.
Or you could use stepconf to build a config and copy one axis over for W if you want software steppers.
I'm glancing over a few details but I think this is doable with only a little trouble and I'm sure you will find help here.

Hmm maybe PNCconf should expand to include UVW axis..

Chris M

Thank you both for the informative replies. I was under the apparently mistaken impression that the 5i20/7i37 was not fast enough for step generation.

I could use a servo, as I already have plenty of new SEM motors and Copley drives. But that would be five axis. I would have to lose one 7I37 or replace the 5i20 with a 5i22 to make room for the extra 7i33. I guess the good news is that I would have extra channels should I decide to add rigid tapping.

If I go with a servo for the knee I would prefer to use a linear scale and not a rotary encoder. Do you think a 5 micron scale would provide enough gain for loop stability (velocity mode with tach)? A 1 micron scale is twice the money.

Doug

Chris;

You must have hit the send button about three seconds ahead of me.

In the process of answering Basher and Andy I realized the servo is probably a better approach anyway. The knee drive can come along after I have the system running. By then I should be comfortable enough with the HAL to do a hand edit.

The board swap is not a significant expense. Not having to install a second power supply for the stepper makes this a more sensible approach. The cabinet is already crowded.

Doug

Doug,
the 7I37 is slow for steppers , however you only need to redirect the stepper pins used to not use the 7I37 .
use a stepper drive with opto isolation built in etc , i.e just come off the back of the idc connections to feed to the stepper , and you will be fine

or you may well find the 7i37 works fine for your needs of course