On Mon, 30 Nov 2020, Viesturs L?cis wrote:
Date: Mon, 30 Nov 2020 22:35:21 +0200
From: "[UTF-8] Viesturs L?cis" <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: "Enhanced Machine Controller (EMC)" <[email protected]>
Subject: [Emc-users] Faulty THCAD board? 7i96 error? Advice needed! Was:
Plasma config with Telwin plasma source
Hello!
I am stuck with the plasma machine that has 7i96 board and also THCAD board.
My biggest issue is getting THC module to work. I have managed to get
the encoder module to receive pulses from THCAD board and to count
them.
Here are the encoder settings:
https://www.picpasteplus.com/v.php?i=b5f8366a2e
The problem is that THCAD board is not sending any pulses with the
frequency division jumper set at 1/1. In that case the rawcounts pin
of encoder module remains at 1. If I move the jumper to 1/32,
rawcounts pin immediately starts to increase and the encoder velocity
is approximately -120.
Thats correct, with the default encoder filter settings you can not
count the ~1/2 usec pulses from the THCAD. That said, for noise
immunity its suggested to use the /32 setting and the default encoder
filtering.
The thing is that I was expecting the value to be 120. But why is it
NEGATIVE?!? I tried setting encoder scale value to be negative. It
fixes the issue of velocity being negative.
Its negative because the counter mode is up/down and the FPGA direction pin
is low if the B input is unconnected (which means down)
Nex problem with THCAD card is that if I fire the plasma and it
creates the arc, encoder velocity decreases. Yes, it gets smaller.
Approximate value is 96 for that particular torch height I have set. I
watched both velocity and position pins of the encoder module.
Position pin was increasing, so the pulses were still coming and it
was not a glitch of a "frozen" value at velocity pin.
My way of circumventing this is negative value for thc.scale_offset
parameter. Then with negative encoder velocity value, which is
decreasing as the plasma starts and negative offset I get positive
voltage value in THC module.
Not sure what you are saying, I would expect the plasma voltage to
decrease once the arc is established (compared to the higher open circuit
voltage)
And then there is a minor problem with 7i96 board:
https://www.picpasteplus.com/v.php?i=f609e19c95
This indicates either poor latency in the host or lost communication with the
7I96. You might go through the standard latency reducing steps on the PC
(disabling power management/speed switching,EIST,C states >C1 etc etc)
Also if you have a Intel Ethernet chip on your PC you need to disable
IRQ coalescing as described in the hm2_eth manual page
This error was triggered a minute or two after I launched the
LinuxCNC. Is that subject to poor config of the system? PC has
mini-ITX board with dualcore Celeron CPU and 4 gab of RAM. Should be
plenty of power for LinuxCNC but apparently I am wrong.
The thing is that after this error HAL pin values were "frozen" and
encoder velocity pin was showing approximately 120 while the position
pin was also frozen and did not change.
Second thing is that I have to use an existing plasma source that they
already have - "Telwin enterprise plasma 160 hf", which is meant for
manual cutting. So there are 2 challenges - get the plasma voltage and
arc-ok signal.
Does anybody happen to know, if the controller board of this machine
has dedicated outputs for these 2 things?
I have connected 2 wires to plasma ground and torch cables
respectively and connected them to THCAD board. I hope that it would
work and not cause too much of EMF noise. Cable is shielded, shield is
connected to ground at a single point with all the other cable
shields.
How do I obtain arc-ok signal? Can I do it in HAL by watching plasma
voltage and trying to assume that it is ok, when voltage drops below
some preset treshold? Or is there a doable way to take a signal that
would drive a relay to trigger input of 7i96?
Viesturs
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Peter Wallace
Mesa Electronics
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