Smoothieware on omtech k40, lightburn not controlling laser power

How do you have the controller wired to the lps?

Generally the L and IN inputs of the lps…

Do you have a pot or manual power control?


I have a Manual control power LED indicator i have connected the same way it came from the factory

If so, then it must have something to do with the pwm control going to the L input of the lps.

It it firing all the time or at specific times or not at all?

Do you have a voltmeter to test that signal?

Do you have a mA meter, if so what does it read when it does fire?

Maybe @lightburn can move this to a seperate thread… This should have been marked solved and a new one created…


Here is a photo my problem is when I put different power from lightburn Example 2 layers #1 power 20% #2 Power 50 The only power that read by the machine is frond the Manually panel not from lightburn i need to Control the power from lightburn, I’m using smothieware board

Did you change the configuration of the pwm port or ?

I’m not that familure with smoothie and it’s configuration, we know they work.

The ‘power’ or pwm on these are feed into the L input (usually). You need some way to check that voltage. Do you?


I will try that but if any body has a video or something to share because im starting in this lasercut life

Do you have a meter?

If so, identify the L terminal of the lps. Can’t see it in the photo…

If you can measure the voltage it should change from say, 20% to 80%. So run it at 20% then run another at 80%. I think that’s inverted, so at 80% you might read 80% of 5v… It should change.

No need for the laser to be enabled. So leave it’s power off, if possible.


Just installed the upgraded board to my machine and after installing the software and added the machine all i get is either machine is busy or alarm lock? has anyone else had this problem?