The printer port isn't dead! (or Linuxcnc is super powerful) (servo content)

I have been hearing all the crap about how printer port is dead, It isn't a stable, yadda yadda yadda..  I think the printer port has had a bad rap because of other control programs.  I have certainly used it extensively with linuxcnc with no issues.  Also - you can get them in pci and pci-e varients any day of the week for <$20 dollars...

Anyway..  Yes - step and direction works great with linuxcnc.  BUT..  You can use the i/o out of the printer port for other cool things...
I have a little emco lathe that I am going to run off the printer port.  Not step/dir but servos closing the loop within linuxcnc...

Linuxcnc outputs pwm to the servo drives - reads encoder position back.  (Linuxcnc closes the PID loop)

Block diagram

You are certainly speed limited by how fast the computer software encoder can count edges..  THis computer can do about 40khz base period.  SO with a little headroom the axis should run at atleast 40ipm.  (the input scale on this setup is 50800 counts per inch)

Here is a proof of concept.



This is using
printer port
BD15A80 AMC drives
Pittman servos with 500 line encoders (2000 count)

I am planning on using X mode which has a good balance of inputs and outputs.

1 in Estop
2 out x pwm
3 out x dir
4 out z pwm
5 out z dir
6 out spindle pwm
7 out spindle dir
8 out drives enable
9 out
10 in x encoder a
11 in x encoder b
12 in z encoder a
13 in z encoder b
14 in spindle encoder a
15 in spindle encoder z
16 in x home
17 in z home

not all parallel ports support X - I have some pci-e ones that don't but some startech pci ones that do..

sam
 

Mesa is certainly way better..    but to get into an industrial closed loop control using just the printer port is pretty inexpensive and awesome...

tommylight wrote:

It's been pronounced dead countless times, but it still refuses to die.
The bad rep is from Mach3/4 as it will push 75kHz through it regardless of the lost steps, so a bad PC with winshit will seem working fine even if it can not output 20kHz that is the minimum mach3 can be set to, so people end up with bad parts. But, if you search the net for days you will not find that as a reason.
Personally, i like the parallel port a lot and still use it, i have machines in daily use for over 10 years, never ever fail.
-
I have also done some experimenting with direct control and it works perfectly for servo control, just search for "cheapest servo drives" and "BST 7960" or whatever those cheap 34A arduino drives are, the latter i have used with parallel port and Mesa 6i25, Mesa works much much smoother. There are videos also on youtube and here on the forum.
I had a Fujitsu-siemens Workstation that could do 75kHz counts, it died recently.
Long live parallel port, from a guy that owns over 20 Mesa boards and used another 30 odd of them!

more mansplaining...