Laser power problem: changing $30 does not seem to have any effect

Hello, I noticed that the value $30 was 255, I then passed it to 1000 to use all the power of my laser. But there are no changes. With constant power activated the power is higher, but at 255 and 1000, the same, no significant changes. I don’t understand,

max S value in lightburn = 1000
grbl v1.1

If you previously had $30=255, while S Value Max was set to 1000, then basically all cut settings above 25% power would have resulted in max power from the laser.

By increasing $30 to 1000, you’re increasing resolution such that only 100% power in cut settings equals 100% from the laser and other values being proportionate to the value.

Note that if your original setting was $30=255, then you’d change S Value Max to 255 rather than the other way around.

Thank you for your answer, I meant: when $30 = 1000 and S Value Max = 1000, there is no real difference with $30 = 255 and S Value Max = 255

Perhaps I didn’t quite understand…

Changing the value of $30 does not change the absolute power available to be used. In effect, it changes the value that represents max power. From there, power is scaled from 0 to the value in $30. In practice, as long as the values in $30 and S Value Max match you should be able to address full power on the laser.

In actuality, for 8-bit Arduino controllers you should stick to 255 for both values as it’s meant to be an 8-bit value represented.

ok… so I have to change my card to have full power with my laser… ?
I have an arduino mega 2560 but the marlin is complicated to adjust the laser signal.
Thank you

No. $30=255 with S Value Max set to 255 should allow you to address the full power of your laser assuming it’s a typical PWM controller laser.

What’s the root issue that you’re trying to address? Sounds like this setting is peripheral to what you’re actually trying to resolve.

Just to use the full puissance of my laser 10w for reduce the time for engraving

Why do you believe you’re not getting the full power from your laser?

Because it was on 255 and I thought it would be more effective for engraving and cutting. With laserGRBL or lightburn in “constant power” mode, it is much more efficient… but because of the difference M3/ M4

Note that Constant Power Mode does not get you more power. It simply does not allow for dynamic adjustment of power to maintain a consistent level of burn. Typically this is not ideal as you’re effectively overburning in those areas. It is, however, useful in certain cases where variable power may be overcompensating.

Is it possible that you are in fact getting full power and expectations need to be reset?

yes, you’re right :wink:

So, i’am trying to put 150% or 200% in “adjuste power” when its engraving. it’s working :sweat_smile:

Are you absolutely certain that your $30 and S Value Max settings are correct?

Can you run this in Console and return output:


yes, $30 and S Value Max settings are correct, both = 1000

I want to make sure I understand the scenario.

In your Cut Settings you’re setting power to 100%. Then in Move window after the job has started you’re manually increasing power to 150% or 200% of the original value and power is continuing to increase?

Or, are you starting at a lower power level in Cut Settings?

I don’t see how the first scenario would work. Can you save the gcode for the job that you’re testing with and post here? You may need to use a .txt extension for the file in order for the forum to accept the file.

you understand, 95% in my Cut Settings and I increase in “move windows”, it works… strange. here the begining of a file (19Mo):
; LightBurn 1.4.01
; GRBL device profile, user origin
; Bounds: X1.17 Y0.16 to X199.65 Y184.91
G00 G17 G40 G21 G54
G0 X-100 Y0
; Image @ 6500 mm/min, 95% power
G0 X92.15Y0.159
; Layer painted black
G1 X2.709F6500S0
G1 X0.559S950
G1 X0.08S0
G1 X0.239S950
G1 X0.08S0
G1 X0.479S950
G1 X0.08S0
G1 X1.039S950
G1 X0.08S0

I can see it working from 95% power up to a certain level. What buttons in Move window are you pressing and how many times? Can you take a screenshot?

Do you get increasing power with every button press or does it stop at some point?

What happens if you start at 100% power?

I have not tested at every press of a button but between 100%, 150% and 200% I see a difference.
Capture d’écran 2023-10-27 104120

Odd. Can you try starting at 100% power and see if you can increase from there?

Sorry, i was not allowed de speak while 4 hours (i’am new here)…
good advise, i’ll try soon, i’ve to go for the week-end. thanks