Another plasma component...

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10 May 2019 00:02 #133309 by phillc54

Uthayne wrote:
Im using a THCAD-300 which requires a voltage offset of 118200. I saw the max (upper) value on the arc-voltage-offset was 99999, so I had to increase it to 120000 so I could set my offset correctly. I realize that range isn't an issue for the THCAD-10s, but I assume anybody else with - 300 would run into the same issue.

I picked an arbitrary number for that, I will increase it to 999999 to hopefully cover all bases.

Cheers, Phill.

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10 May 2019 00:06 #133310 by Grotius
Replied by Grotius on topic Another plasma component...
@Bryan,

If you open up your Hypertherm inverter you wll find a dip switch. Here you can set several divided arc value's for CPC port.
So this is nice.

If your mesa has a input of max 300volt dc i would use problably the 20 : 1 to stay at high resolution when using only CPC !



In the threat of John. you can download the user manual forum.linuxcnc.org/plasma-laser/36538-pierce-height
section 7-6 has the info.
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10 May 2019 00:10 #133311 by phillc54

JTknives wrote: So when I trip the ohmic or floating z switch after I run m03s1 I get a error saying “ohmic probe/floating switch detected before probing program is paused”

If you have an older version and the ohmic probe led was off when probing started that is most probably your probe height is too low, it is calculated from the Z minimum limit.
If the ohmic probe led was on before probing started then it means the probe is already tripped.
Newer versions have better error messages.

Cheers, Phill.

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10 May 2019 02:05 #133312 by rodw
Replied by rodw on topic Another plasma component...

Uthayne wrote:
Ah, good points. Thanks Grotius and rodw.

Is there any benefit to switching it out for the -10 model? Was previously using it with raw arc voltage, now using it on a Hypertherm and could use divided voltage straight from the CPC


Possibly. If you use the raw arc voltage on the Hypertherm, there will be a couple of extra resistors in the circuit which will distort the readings (100k on each leg I think). I think though you could calculate the divider ratio on the assumption of the resistance required for a 300 volt full scale per the thcad manual and then add 200k to it and recalculate the fullscale and divider ratio from there.

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10 May 2019 04:30 #133321 by JTknives
I noticed you mentioned pid and steppers. In my file I have a callout for PID stuff but I’m running steppers. I wonder if that’s causing problems. The thing the bugs me the most is I’m trying to wrap my head around how everything is programmed so I don’t have to keep asking questions.

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10 May 2019 04:48 #133323 by JTknives

rodw wrote:

Uthayne wrote:
Ah, good points. Thanks Grotius and rodw.

Is there any benefit to switching it out for the -10 model? Was previously using it with raw arc voltage, now using it on a Hypertherm and could use divided voltage straight from the CPC


Possibly. If you use the raw arc voltage on the Hypertherm, there will be a couple of extra resistors in the circuit which will distort the readings (100k on each leg I think). I think though you could calculate the divider ratio on the assumption of the resistance required for a 300 volt full scale per the thcad manual and then add 200k to it and recalculate the fullscale and divider ratio from there.


From what I have seen the THCAD reads ua (micro amps) not volts. This is why voltage deviders can mess with it. It does not care what the voltage is it just looks at the microamps that the voltage creates running through the resistors. The the THCADs are designed to read 0-100 micro amps. The higher the resistance in the circuit the higher the voltage can be and put out the same amps. If your using the THCAD300 then it has the resistance it needs built in to reach full scale of 100 micro amps at 300volts. If the hypertherm has 100k in line on both legs then it will mess with your scaling. To show you why let’s do some math. 300v/.0001amps=3,000,000ohms. So the THCAD has 3 mega ohms built in. If you toss another 200k into the mix your at 3,200,000 so 300v/3,200,000=0.00009375Amps. So 300v would only give you 93.75 microamps not 100. 93.75/100=93.75%x300=281.25. So at 300v the THCAD will think your at 281.25v

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10 May 2019 05:17 #133326 by rodw
Replied by rodw on topic Another plasma component...
Well with a bit of luck if you take the 1/32 0 volt reading from the 1/32 full scale and you might end up with about 25000
divide 281.25 by that number and that should be your scale figure (around 0.01125) and the 1/32 0 volt reading will be your offset. But just check the resistance on your raw arc voltage first. Hope I got that right as I bypassed Phills settings.

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10 May 2019 05:53 #133329 by JTknives
Oh and if your wondering why hypertherm builds 100k resistors into the raw source. 300v/100,000=.003ma so non lethal. 5ma is accepted as maximum harmless current. It also takes 500v to reach that current when In contact with human skin. So 300v@3ma I bet you would not feel besides a mild tingle. No company in their right mind would send raw arc voltage down an exposed cable.

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10 May 2019 06:14 #133330 by phillc54
I have pushed a few updates.

plasmac.comp file was modified so you will need to run make.

IHS skip type determined by THC enabled/disabled.
Changed files are:
hal/components/plasmac.comp

configs/sim/gmoccapy/plasmac/README.md

configs/sim/gmoccapy/plasmac/imperial_plasmac.ini
configs/sim/gmoccapy/plasmac/metric_plasmac.ini
configs/sim/gmoccapy/plasmac/plasmac.hal
configs/sim/gmoccapy/plasmac/plasmac_run.hal

nc_files/plasmac/imperial_ihs_skip_0.ngc
nc_files/plasmac/imperial_ihs_skip_1.ngc
nc_files/plasmac/metric_ihs_skip_0.ngc
nc_files/plasmac/metric_ihs_skip_1.ngc


Increase range of arc-voltage offset and scale.
Changed files are:
/configs/sim/gmoccapy/plasmac/plasmac_config.py


Add THC start delay.
Changed files are:
hal/components/plasmac.comp

configs/sim/gmoccapy/plasmac/plasmac_monitor.glade
configs/sim/gmoccapy/plasmac/plasmac_monitor.hal
configs/sim/gmoccapy/plasmac/plasmac_run.glade
configs/sim/gmoccapy/plasmac/plasmac_run.hal
configs/sim/gmoccapy/plasmac/plasmac_run.py


Remove redundant indicators.
Changed files are:
configs/sim/gmoccapy/plasmac/plasmac_monitor.glade
configs/sim/gmoccapy/plasmac/plasmac_monitor.hal
configs/sim/gmoccapy/plasmac/plasmac_monitor.py
configs/sim/gmoccapy/plasmac/plasmac_run.glade
configs/sim/gmoccapy/plasmac/plasmac_run.hal


Cheers, Phill.

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10 May 2019 07:32 - 10 May 2019 07:32 #133335 by rodw
Replied by rodw on topic Another plasma component...
Phill, Got his installed. I noticed we lost the nice colour coded enable/disable button.
I also hit estop straight after a probe with torch disabled and it was about 1.0mm too high
Then did the same in a live cut and it was about 2.0mm too high
Using Ohmic sensing
Is there an adjustment for this height anywhere?
First time I tried that. I'll check my float switch offsets in case its using it

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Last edit: 10 May 2019 07:32 by rodw.

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