Switch relay in a defined x position

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14 Jan 2022 20:53 #231793 by mgm
Good evening,

Since my X axis is 2800 mm long I have built a pneumatic support. This is mounted in the middle. 

What I want now is the following:
When the X axis arrives at 1000 mm, a relay should be switched to high and at 1800 mm switch back to low so that the axis can pass through.

Is there a pin or a signal that I can use for this?

Moderator: if wrong here please move

Cheers
Micha

 

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14 Jan 2022 21:07 - 14 Jan 2022 21:08 #231796 by rodw
Its best to do this in a component that monitors the axis.x.pos-cmd
Here is an example that triggers a relay if the position is > a specific location set by a pin. If you added a second pin, to turn the output off, you would jjust need to change the if statement
 
param rw  float cutoff    "Absolute axis coordinate above which disables zone change"; 
....
if((position > cutover) && (position < cutoff))

YOu may need to change when position is set to 0 or 1 to suit your needs
 

File Attachment:

File Name: downdraft.comp
File Size:1 KB
Attachments:
Last edit: 14 Jan 2022 21:08 by rodw.

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14 Jan 2022 21:23 #231801 by mgm
Hello Rod,
thanks for your answer, this is exactly what I was looking for.
Please explain me now how and where I can include this.

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14 Jan 2022 21:32 #231803 by rodw
sudo apt-get install downdraft.comp
and add the suggested hal connections.
Check the main docs for details on using the "hal component generator" (halcompile)

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14 Jan 2022 21:45 #231806 by mgm
Thanks for this information, will do.
Best
Micha

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16 Jan 2022 13:48 #232014 by mgm
Hello Rod,

I have now tried to test your suggestion.
Unfortunately, I get along with it at all.
It fails already with the fact that I cannot find the correct directory:
"Place the .comp file in the source directory linuxcnc/src/hal/ components and re-run make. Comp files are automatically detected by the build system."

I am using Linum MX and 2.9 for testing, in a VirtualBox.

I installed it according to this manual:
LinuxCNC Install using MX Linux 19.4 - Geared Toward New/Windows Users

What am I doing wrong?

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16 Jan 2022 18:42 #232043 by rodw
Oops I was totally wrong above. There is no need to copy the file to any special location

For a rip build type this in the folder the comp file is in
halcompile --install downdraft.comp

For a deb install add sudo to the command above.
sudo halcompile --install downdraft.comp

See linuxcnc.org/docs/devel/html/hal/comp.html


You can change the file name but you also need to edit the first line in the file to use the new file name

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16 Jan 2022 22:16 #232074 by andypugh
Isn't this something that the built-on "comp" or "wcomp" components can do?

linuxcnc.org/docs/2.8/html/man/man9/comp.9.html
linuxcnc.org/docs/2.8/html/man/man9/wcomp.9.html
The following user(s) said Thank You: hoffb77

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17 Jan 2022 06:27 #232091 by rodw

Isn't this something that the built-on "comp" or "wcomp" components can do?

linuxcnc.org/docs/2.8/html/man/man9/comp.9.html
linuxcnc.org/docs/2.8/html/man/man9/wcomp.9.html

No wonder I wrote a component. The documentation there is truly awful. UNnless you have an electronics major you have no  clue what a comparator is.

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17 Jan 2022 18:10 #232148 by mgm
I have now managed to do this with the Halcompile. As an answer I got:

compiling realtime downdraft.c
Linking downdraft.so
cp downdraft.so /usr/lib/linuxcnc/modules/

I have also added the lines in the Hal file.

Now when I start Linuxcnc I get this error message:
HAL-ERROR: function downdraft not found!

What or where is the wrong?

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