Appropriate Power Settings on K40


I have a digital K40 that’s stock. Just ordered a mini Gerbil and LightBurn. I’ve been watching some Lightburn tutorial videos and havent came across any that describes what the machine should be set at while using Lightburn. Obviously with the mini gerbil the controller will adjust power in software.

Do I just set the K40s power to 100%? If not can someone please explain how to determine the correct setting or supply a link describing how to handle this?

(Paul) #2

Hi Speedster1, The Mini Gerbil has a setting for the power range. LightBurn will use that for 100% power. The default configuration for the power range is set with $31. In LightBurn you can read out the controller settings via command $$ in the LightBurn console. You can configure it via the command $31=1000 (default setting). Higher e.g. 2000 means more resolution in the laser power.
Hope this helps, also there is an explanation of the settings here


Thanks for replying Paul. I’m still confused about how this works though. Maybe I’ll understand it a bit more once I get it installed and setup.

Are you saying that the power shown on the digital display will not effect anything becuase the power setting will now all be controlled in software? No difference if I put the digital display on 50% vs 10%?

I installed a 30mA ammeter today so that I had an idea if I had been overworking the laser. At 10% power on the laser it was drawing about 6mA. At 60% power it drawed 18mA. If I determine that 20mA is the absolute max I want to draw do I set a parameter in lightburn that makes 100% power equal to the 20mA setting?

(Paul) #4

Hi Speedster1, I was mistaken… apologies. $30 is the power range. If you set it to 2000 then it matches 20mA on full power. $31 is the min power, just set it to e.g. 0 or 5

In LightBurn you need to set the value as well.

(Claudio Prezzi) #5

@Speedster1 The value you set on the digital panel of your K40 defines the maximum power that is used. This defines how mucht 100% in the software is. The software then defines how much power between 0 and this 100% is used.
The $30 configuration of the firmware only defines which number should represent 100%. Usually this is set to 1000.


Perfect. That’s the info I was looking for. Basically if I determine that 70% on my digital panel corresponds to 20mA then I just leave the K40 set to that value. And any subsequent power adjustments are done in Lightburn?

I’ve heard conflicting info but it seems the consensus is that I should drive the laser harder than 20mA. Is this correct?

(Claudio Prezzi) #7

Yes, that’s correct.
20mA is about the max that the K40 laser tube can handle (without much lifespan degrading).

You probably also hear something about lowering that setting because of grayscale resolution, but this is related to 8 bit grbl. Gerbil has 16 bit PWM resolution, so no problem with that.

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