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Changing Power settings (S Value)

I've looked at several posts and they have only served to confuse me further on this subject and I've had people insist that I have to set my hard limit on the laser control panel.  I don't know how many times I've had to explain that in order to hook up the PWM for the Mini Gerbil on my particular power supply, I had to totally disconnect my power control board, yet they keep telling me I CAN set it on the panel (which is DEAD... because I can't plug it in... because the PWM wire is there...).  That leaves controlling max power to the Mini Gerbil and/or Lightburn.  I understand this can be done with S Value.  Right now, the default S Value of 1000 is set in Lightburn and likely in the Mini Gerbil since I've never changed it.  When looking at the current percentages, it appears to be about the same as the old power panel where I NEVER want to go over 50% or I'll drive the laser tube too hard.  What do I set Lightburn and/or the Mini Gerbil to in order to limit my max power from the PSU to 50% but assign percentages of 0-100% of the 50% max within my layers?

Hi Rob,

You can leave the LightBurn setting for S as 1000 and set the Mini Gerbil S max parm to a higher value (means a longer range) e.g. 2000. That means when Lightburn issues a full power S parm (S=1000) that MiniGerbil sees it as half the range (2000).

If this is practical is another question. For just cutting I would think yes but for engraving is might give very light engravings. You probably need to do a bit a=of trial and error.

Note that the gasses in the tube do deteriorate with time. So no use of light use will still give a false impression that the tube will last twice as long. A better insurance is a good brand tube e.g. Reci tube.

Hope this helps.

Cheers, Paul awesome.tech

Thanks Paul.  It seems pretty accepted across the board that a stock K40 tube shouldn't be pushed over about 16mA.  At least this is what I've been lead to believe over the last couple of years and seems to ring true with videos I've see of people hitting the test button with the digital panel set at 90 or greater and then suddenly their tube fails.  Has this not been your experience?  I'm genuinely interested in what's best for a balance between good results and longevity of the tube, so recommendations are welcome.  I do want a good image etch, but I do an awful lot of cutting too.  I don't even mind setting a macro or two for optimized cutting vs. optimized image rastering to make the switch easier if that's recommended.  I still don't really understand all the options for images in Lightburn yet.  Pointers there are welcome too.

Hi Rob, yes my experience is to not push it over 16mA. I usually cut 3mm acrylic at 8mA and a few passes. Often clean the mirrors because they do get dusty quickly and align them well.

The tubes do last between 500 and 2000 hrs. My tube was gone within 2 months because it was probably old stock. It never did cut well. The second tube was a reci tube which lasted two years and did cut well. The new tube I got now went in a few weeks ago so will see. Maybe keeping a log for the hours might be a good idea.


Cheers, Paul awesome.tech

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