I need to use my mill manually while I am converting it to EMC. Because
the spindle VFD is mounted at the back of the mill and I removed the
DRO, I decided to just hook the linear encoders and the VFD to my Pico
UPC and use EMC as a DRO and VFD controller. I figured, no big deal, put
the hand-wheels back on, a little wiring, start EMC, unset E-stop,
controller on, MDI, s1000 m3 and go. So far so good. The spindle is
turning, I grab the X hand-wheel, give it a turn and ... the spindle
stops and I get a following error. Dooh.

I looked at my .hal files to see if I could change anything to keep from
getting following errors while still having EMC on. Nothing easy came to
mind, so I did a search on linuxcnc.org for "DRO" and found this:

http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?PyVCP

>From this, I created these:

http://www.wallacecompany.com/machine_shop/bridgeport/pyvcp-dro2-bp2.hal
http://www.wallacecompany.com/machine_shop/bridgeport/pyvcp-dro2-bp2.xml

I haven't tried the DRO/VFD program in the shop yet. I commented the
ppmc lines out, so I could run it in my office without the UPC. All that
works are the spindle buttons. If you want to run it, just copy these
two files to your /home/your_user_name/emc2 directory, From a terminal
window, cd to home/your_user_name/emc2 and run: 

"halrun pyvcp-dro2-bp2.hal &". 

Another window should come up with the DRO in it. The ampersand at the
end of the command will let you go back the the terminal window and run:

"halmeter &"

as many times as you need for looking at the state of signals, pins and
parameters.

If anyone has suggestions on how to make this better, please let me
know. It would be nice to get a complete list of tags available for
the .xml file and how the number format tag works.

It shouldn't be too difficult to study the original to get it to work
with a parallel port and software encoder. The tricky part will be in
coming up with a DAC for the VFD. I first thing that comes to mind is a
dual parallel port card to provide the six input pins for three
encoders. For the VFD analog in, use eight output pins to a DAC chip
(plus one for an output enable?) and 10 Volt power supply. For the
Forward and Reverse, two more output pins and a pair of opto-isolators
to sink the VFD inputs. Easy-peasy-lemon-squeezy, right?

-- 
Kirk Wallace (California, USA
http://www.wallacecompany.com/machine_shop/ 
Hardinge HNC lathe,
Bridgeport mill conversion, doing XY now,
Zubal lathe conversion pending)


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