On Tue, 26 Mar 2019, Gene Heskett wrote:
Date: Tue, 26 Mar 2019 08:03:17 -0400
From: Gene Heskett <ghesk...@shentel.net>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Rock64 pre-orders on Banggood.
On Tuesday 26 March 2019 07:19:19 andy pugh wrote:
On Tue, 26 Mar 2019 at 06:35, Chris Albertson
<albertson.ch...@gmail.com> wrote:
The loops do need data. They need a target position or a target
velocity. These targets are sent across an SPI (or I2C or Ethernet
or,..) interface from a Linux machine. But you MUST de-couple the
timing. Linux can not be feeding one target number at a time.
Drawing the boundary becomes more difficult when you add in probing,
threading and spindle-synchronised motion.
And it appears I may have to put a C1G rev4 back in service just for
limit and home switches, the 7i76 takes too long to recognize a closed
home switch.
I dont think this is true, motion only samples the home switches at the servo
thread rate so there is no speed advantage of sampling the inputs at the base
thread.
How wide is the home switch pulse at 120 degrees/sec?
less than 1 ms seems unlikely...
I've not more than though of it, but have wondered if it would be
possible to set up a 10 kilohertz base thread that accessed the parport,
while leaving the 1 kilohertz stuff on the 7i76? I just had to slow the
home_search to 120 degrees a sec to get a rotary's home switch to be
recognized, otherwise it just sails on by. By putting the home/limit
switches on the parport, limiting me to 5 switches which is not enough,
would any response time be gained?
I got the home switches I ordered yesterday, but I can readily see that
they are going to have to be mounted on a springy material, seriously
complicating the switch mount, otherwise they'll be smashed flatter than
a coors can before the machine can get stopped. Or I use search_vels no
faster than cutting vels if even that fast. This machine, with its puny
motors, can still make x-y moves slightly above 200 ipm. I will probably
set the homes as I intended, but it means I'll have to use very
leasurely homeing moves. After switch closure, I'll have about 10 thou
to get stopped before a hard smash stop. To rig more clearance means
some elastomeric on the frame to cushion the button push. That will
imply glue to hold it in place failures... Not what I intended when I
ordered 100 of this switch for <$3.
I also rxed the bigger cable chains, and got one of them installed before
dinner last night, one to go. Otherwise no room left for switch wiring.
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)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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Mesa Electronics
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