Camera setup

Forgive me if this is obvious but I can't immediately find the answer.  I would like to add a camera to the latest Qtplasmac but am confused as to how to enable it?  Also, are there any recommendations as to a USB camera that is know to play nicely with the system?

Many thanks

The camera is enabled if a Peripheral Offset has been applied for a camera.
See the Camera and Peripheral Offset sections in the manual.
I used a cheap "endoscope" camera for testing.
TBH I think a laser crosshair is a better proposition for sheet alignment on a plasma table.

Many thanks - I have one of those so will have a go - I take the point about the laser as well.

phillc54 wrote:

TBH I think a laser crosshair is a better proposition for sheet alignment on a plasma table.

100% agree.
On many plasma tables the 5m limit for USB cable length is far too short without adding repeaters etc and often if using a mesa card, the PC is not co-located with the controlbox where the rest of the wiring comes from so routing the wiring gets messy.

To add a laser, you likely already have power up where the torch is so its easy to add (even if you need to add a $3.00 24v to 5v step down power supply). I did not have a spare wire in the cable so could not get qtplasmac to turn it on so added a small switch up on the gantry. But more often than not, the laser is just left on.

Finally, with plasma, pinpoint accuracy is not required when setting the zero point so a 1-2mm laser dot is more than sufficient. Steel sheets are usually about 5mm over size so close enough is good enough!

There is some interesting recent discussion on camera equipment over on Plasma Spider, here:

plasmaspider.com/viewtopic.php?f=147&t=34918

As a Canadian, I am constantly punished by high shipping rates and border concerns for importing goods from the states, so rather than order the products linked in that thread, I ordered this active USB extension cable from Amazon Canada. I have a Supereyes camera here that I'll try. At the computer side, I'll plug the cable into a powered USB hub. I don't have a short-term goal to get Scanything working with LinuxCNC Master, although long-term that would be nice, so I think the camera I have should be fine for this. I'll try to remember to report back with how it goes -- or fails, as the case may be.

Just a bit more about the USB hub. I hope this will accomplish two things: (1) provide more power to the active cable, and (2) help isolate the USB cable and the harsh electrical environment it's in from the computer.

I spent some time with my long USB cable and the Supereyes camera this evening. I can display a video feed from the camera in VLC player just fine. However, when I hit the Camera button in QtPlasmaC, it uses the computer's built-in webcam. (I am using an older Dell all-in-one computer, which is just laptop-grade hardware and not optimal but it was a cheap way for me to get a touchscreen.)

In VLC, the built-in webcam is /dev/video0 and my USB camera is /dev/video2. How can I specify which camera is used by LinuxCNC rather than allowing it to pick system default? I tried, so far unsuccessfully, to disable the built-in camera via udev rules.

Are you running LinuxCNC from a package or from a run in place build.
 

I'm running a package install.

If you want you can try the following.

You could edit the handler file /user/share/qtvcp/screens/qtplasmac/qtplasmac_handler.py
and add the highlighted line, you need to be root user to do this:
 

When you run QtPlasmaC then it will add a camera port entry to the [CAMERA_OFFSET] section of qtplasmac.prefs in your config directory.
 

Close QtPlasmac
Edit qtplasmac.prefs and change the number to suit the required camera.
Restart QtPlasmaC
I don't know if the python3-opencv camera numbers map the same as VLC numbers so it may be a bit of trial and error. My test rig has the same numbers for both but they are reversed...

If it works OK for you we could add something like this permanently.