Opinions on Hard mA Limits (K40)

My ammeter arrived today and I made a new control panel for my laser. Until this point, I left the hard limit on the laser at 70% (thinking that was a safe margin), and I let LightBurn do the rest. Well, it turns out, 70% and above is roughly 100%. All %s over 70 gives 25mA, which is a little surprising, as I didn’t think it could go that high.

Honestly, this is a theoretical musing more than anything. Even with the hard limit at 70% (aka 99%), I never go above 55% in LightBurn. I haven’t needed to.

I’ve read opinions on the interwebs saying to keep the hard limit between 16 to 18mA. What do you folks think?


This is what my control panel looks like now:

I have felt safest with a maximum of 16 mA as far as the tube is concerned. The power does not increase anymore after 16-17mA, I have tested it several times. The curve does not rise linearly to approx. 17mA, then it just gets flat.
Your panel looks great.

… when switching from M2 to Mini-Gerbil, the original K40 power potentiometer itself loses its function completely. If you want to limit the power on the hardware then the output from the PSU must be regulated, this is not possible on a (standard) K40 / PSU.

I have the K40+ from OMtech, not Mini Gerbil. The control pad still works to limit the power. about 72% and above is 25mA, but if I drop from there the max power drops too. at 50% it’s about 18mA.