ohm sensor

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12 Jan 2022 11:49 #231555 by chuben
ohm sensor was created by chuben
Hello:
I'm building a plasma table and I don't know how to make the ohm senor work.
The plan of my installation is the one I attach. I have downloaded the firmware so that the two encoders work but when executing Pnconfig I don't know which pins to associate with each output.
Can someone tell me how to do it or tell me if there is a tutorial to see it?
Thanks 

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12 Jan 2022 12:13 #231557 by tommylight
Replied by tommylight on topic ohm sensor
Moved to "plasma and laser"

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12 Jan 2022 12:14 #231558 by rodw
Replied by rodw on topic ohm sensor
I don't think pncconf knows about the Hypersensing using the THCAD-5 so you will have to do it by hand.
There is a component you can use which describes the required pins.
linuxcnc.org/docs/devel/html/man/man9/ohmic.9.html

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12 Jan 2022 12:45 - 13 Jan 2022 11:01 #231560 by snowgoer540
Replied by snowgoer540 on topic ohm sensor

Hello:
I'm building a plasma table and I don't know how to make the ohm senor work.
The plan of my installation is the one I attach. I have downloaded the firmware so that the two encoders work but when executing Pnconfig I don't know which pins to associate with each output.
Can someone tell me how to do it or tell me if there is a tutorial to see it?
Thanks 


Since you haven't implemented it yet, save yourself the hassle and skip THCAD ohmic sensing.

Phill did a nice write up on THCAD vs Relay ohmic sensing (and you can find a schematic to use the relay method there, which you can use pncconf to set up): here

The setup is way less complicated especially for someone new to the scene, and there is way less fiddling to get it to work, no components to install, it's cheaper, and its not bothered by noise/interference, and those of us who have ditched THCAD ohmic have found relay ohmic to be way more reliable, etc. It just works, right out of the box.


Otherwise, there are a lot of threads of people wading through THCAD ohmic trying to get it set up and working, so I'd clear some time for reading through those. Be ready for installing different versions of the component linked in the previous reply, head scratching, halscope plotting, random gremlins, false probes, missed probes, etc. That said, a few people seem to enjoy it.
Last edit: 13 Jan 2022 11:01 by snowgoer540. Reason: fixed link
The following user(s) said Thank You: Aciera

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21 Jan 2022 20:10 #232677 by chuben
Replied by chuben on topic ohm sensor
I've done what I've been told but I can't get the ohm probe to work. In the attached file I send you my INI and HAL configuration in case anyone can review it and give me a hand. Thanks 

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File Name: custom.hal
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File Name: custom_postgui.hal
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File Name: PLASMA_Lin...hine.hal
File Size:15 KB
 

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File Name: shutdown.hal
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File Name: custom_postgui.hal
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File Name: custom.hal
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File Name: shutdown.hal
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File Attachment:

File Name: PLASMA_Lin...hine.hal
File Size:15 KB
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24 Jan 2022 14:12 #232962 by chuben
Replied by chuben on topic ohm sensor
Hello, can anyone help me?

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24 Jan 2022 18:38 #232994 by paulsao
Replied by paulsao on topic ohm sensor
And the ini file? Should you also give the circuit you are making?

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24 Jan 2022 20:18 #233005 by chuben
Replied by chuben on topic ohm sensor

And the ini file? Should you also give the circuit you are making?
The circuit is in the first post.
 

File Attachment:

File Name: PLASMA_Lin...hine.ini
File Size:6 KB

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24 Jan 2022 20:44 #233009 by rodw
Replied by rodw on topic ohm sensor
It would seem a couple of key lines are commented out. Plasmac/QTplasmac has had many changes so there is no guarantee the example in the docs is still correct.
#net ohmic-true ohmicsense.ohmic-on => db_ohmic.in
#net plasmac:ohmic-enable => ohmicsense.is-probing
The first one is the actual probe signal so it must be connected or nothing will work.
The second one is the enable signal so it should be connected too.
You need to start with some trouble shooting. Is the encoder velocity changing at rest?
If you touch the tip to the material with a jog wheel, do you see voltages on the respective pins of the component?
This is where halshow is your friend. Watch all of the ohmic sense pins

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24 Jan 2022 21:13 #233013 by chuben
Replied by chuben on topic ohm sensor
I have everything connected as it says in the schematic of the first post but then when I do Pnconfig I don't know which pins to enable.
When I touch the tip to the table the voltages change from 0 to 24v.
Sorry for asking so much but I can't get it to work.
Thanks

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