Hi,my laser power is always on high, i got my settings svalue 1000 and $30=1000 but even if i set 10% power it does 100%,so what can i do?

Hi,my laser power is always on high, i got my settings svalue 1000 and $30=1000 but even if i set 10% power it does 100%,so what can i do?

What do you have it set to in the layer?

Can you drive and do you have a voltmeter…

It’s easy to check the pwm control line for proper operation…


Hi,thanks to respond, i got 3000 speed and 60% max power,tab size 0.50,even spacing 50.0,tabs per shape 1,and limit max tabs 1,and yes i do have a tester

You can measure the pwm output of the controller to see if it’s working correctly…

If it’s a ttl signal (most are) it should measure a percentage of it’s 5V supply… at 50% power, it should read 2.5V at 20% power 1V…

If it’s working, the it’s after that or probably the laser module… if it’s not working I’d check the configuration is correct for $30 and S-Value Max.

If the settings are correct, the controller may have a problem.

Make sense?


Have you selected GRBL (not GRBL-M3) as the device profile when setting up your engraver?

Is this a custom build?

Please request the the following reports by entering this in the Console window in LightBurn:
Pressing enter after each one.

Hi,thanks again for your answer, ok i try to tested through the fire bottom and it shows 12.26v before hit it and 10.21 when is on fire and still the same from 20% to 0% cuz i don’t know how to test it,i have 0 knowledge on electronics by the way when i burn a text my laser starts on before get to the letters and doesn’t turn off between letters so is like drawing without lifting the pencil, can you tell me how i can post a picture?

Hi Jonn,yes i pick up GRBL but i don’t know the brand from this machine cuz i bought it from china and they have the same machine with diferent brands like lunyee,vevor so i select custon

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If you are reading from ground to the pwm signal, anything above about 3V will turn on the laser.

Ensure you are measuring from ground to the pwm signal…

At these values it should be on all the time.


Well i connect my tester on the wires goes into the laser module wich comes the first reading and them a hit fire them it comes the second reading

You must not be reading the ttl pwm… This is a 0 to 5V signal… Although, some modules do allow the voltage to exceed 5V, but it still reads it as ttl, so anything over about 2.5V is on… Meaning all of the measured voltages would turn the laser on…

You are measuring from ground to the ttl, not ground to V+?

If you unplug the laser module, and measure what’s coming from the controller do you get different measurements?


This is common when the Manufacturer of the controller is also selling CNC machines with a spindle motor or a router for cutting wood or metal.

It is common practice to let the spindle not stop when moving from place to place but for a laser, the laser must stop.

$32=1 is the laser mode. $32=0 is for CNC machines with a spindle motor that must remain running.

$31= 0 (or 1 usually)

The value assigned to $30 in your engraver should match the value assigned to S-value max (in Device Settings)


I suspect that it might be a voltage drop from light, underspec or damaged wiring.

Start a new project in LightBurn,
draw a small square near the Origin.
Click File, click Save GCode, save this unusual file somewhere convenient.

Change the filename so it ends .txt and drag it into a reply here.

If the File is only 20 Lines or so you can copy and paste all the text into a reply.

This will tell us if LightBurn is commanding the Laser on, or if the Laser is Stuck on because of an inaccurate setting or a hardware issue.

I got 12.33v

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