Preview & Job Monitoring - Co2 laser

Hi, I’m new to LB. installed it last night for testing my soon to be upgraded K40D with Smoothieboard. this was the fastest successful bench test ever. launch LB, connect to smoothie, hit start. works like a charm.

Few quick questions if i may:

  1. If possible, How can i sync Preview screen with actual running job? or at least see the laser head location during a running job?

  2. Is it possible to configure LB to command Smoothie to turn on an additional onboard FET to be on whenever laser is on, regardless of the power? the FET should be like: above 1% = ON, below 1%= OFF.


  1. You can look at the laser. Sorry this sounds cheeky, but it’s the correct answer. You should absolutely not leave a laser unsupervised, as they make fire as part of their normal operation, and I’ve seen many, many pictures of burned machines with captions like “I had to pee”. I very strongly resist the addition of features that are solely for remote monitoring.

  2. Not at this time, no - This is the first such request I’ve ever gotten. You might be able to do this within Smoothieware’s configuration somehow, but I can’t say for sure. What would this be used for?

Hi Oz, Thx for replying.
I do not leave my laser unattended. my LB is just beside the cutter and I have no intention to leave the room while laser is doing its thing. this brings me to my second question which emphasizes my wish for more safety features. it happened that my laser was on when parked at the home location and since there was a black media to cut on bed i did not see it was on. it drilled a hole and there was no clear sign it was on. This made me promise to myself to mount a red led on top of the laser head or around the bed to make it absolutely clear the laser is on even at 1% & or less power - only when laser is completely off this led should turn off. i hope you will find this important enough to add this feature to LB.


You could be using either a strange version of Smoothieware, or the wrong build, because there is no way that I know of to have Smoothieware leave the laser beam on if the head is not moving.

Smoothieware varies the laser output by the speed of the head. If the head is stopped, the laser is turned off completely. Do you have Smoothieware configured for laser, or are you using a spindle or fan output? I’ve heard of people doing this, but it’s obviously unsafe.

Hello again Oz.
Can we at least agree that this safety feature will be nice to have? to configure LB to turn on a second fet on main board according to my suggestion above, e.g - Turn ON Fet2 whenever fan output is even slightly above “0” and to turn FET2 (maybe bed heater fet?), off when fan output is “0” (lowest pwm)? I am still checking if snoothieware can do this natively by editing the config file but i doubt it. we shell see. BTW, I was testing smoothieware device - this one has no way of changing M106 / M3 / M5 / etc…). My laser output is on FAN output and the fet led flashing as it should.

I am using SKR 1.3, LB auto find it as Smoothieware board (gcode) but no control over gcode commands. maybe I should manually configure it differently?..

I honestly have no idea how to go about doing that. Your laser should absolutely not be on fan output - There is a dedicated laser module in the Smoothieware code that manages the laser PWM output, and turns it off automatically when the laser stops moving. Please read the laser configuration page on Smoothieware here:

1 Like

Thank you Oz.
I am sorry LB probably wont support this so basic safety feature. i will ask around Smoothie guys and hopefully this will be possible to add to the firmware/settings.

Bench Testing LB for two days now and its really nice.
Keep up the good work.

Found this in Smoothieware flavor for lasers (the firmware I’m currently running): "laser_module_ttl_pin"
# This pin turns on when the laser turns on, and off when the laser turns off.

This might just do the trick for me.
I will check and if so - I’m happy.


This is to confirm my findings.
"laser_module_ttl_pin" does the trick. pin leg goes high regardless of laser power - exactly what i was after.

Smoothieware flavor for lasers? Are you referring to the CNC build of the official firmware?

Yes, I am running this one. so far, so good, but more tests are called for.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.