Laser Scaling Issues

I am trying to get Lightburns 0-100% power scaling to match my output power.

Example: If I command 100% power in Lightburn I get 18mA but if I command 50% power I get 12mA vs 9mA. This has caused issues on my low power end by being way too powerful when down at sub 1% power. I am thinking this is the firmware on my C3D card setting?

I am unsure where to turn, any help is appreciated.

If you want 100% in lightburn to be 100% true power, set the potentiometer or front panel to a value that corresponds with 100% power on your tube. Then, power will scale more or less linearly(*) from 0 to 100%.

Note that voltage-excited CO2 tube power output is not linear. For instance, most won’t even fire at all until >6% power is reached - some as high as 11%. The power output increases pretty rapidly to around the 35% mark and then slopes slowly thereafter to 100%. And, no two tubes are the same! Unfortunately this is something that will take a bit of playing around with to get right.

Thank you for your response!

I have my K40 limited to max at 18mA so that no matter what the software or firmware command I can only ever see a max of 18mA. My goal is to have the software when I command 50% to give me 9mA. I am less concerned about the laser energy performance as I have no means to measure that. I am guessing there is something in the firmware of the C3D that is scaling the input that is received from Lightburn.

That’s the thing - the power output isn’t linear, so setting it to 50% probably won’t equal 9 mA. There’s no scaling going on inside the controller.

So when I am commanding in the software 50% power your telling me there is nothing scaling the output to a field device that has some real world range?

That’s correct - commanding 50% power is a 50% PWM duty cycle on the output/laser trigger pin. That is linear from 0-100% power and maps to 0-100% duty cycle exactly with no prescaling or filtering done whatsoever.

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Setting the “pot” in mine it’s digital but all the same to 100 and then trying to allow the software to scale also didn’t work. The only way I can find the get low end control is to move the pot down low. Doesn’t seem right but I just don’t know the architecture that well.

@staff Do you have any input?