Newbie Question

I’m sure this is and incredibly elementary question, but here goes anyway. I have been using a stock K40 for a couple of years now. That includes Corel Draw (with Corel Laser). I’ve just recently seen the light and upgraded everything…tube, lens, power supply, controller board (Mini Gerbil), computer, and of course, the software (LightBurn).

In the Corel Laser world, I would control speed in the software, but power was controlled manually using the potentiometer/ammeter on the machine. Now, in LightBurn, I understand that I set the power in the software…which is great.

Here is my question - since LightBurn is controlling power, do I just keep the power potentiometer on the laser turned all the way up all of the time? In the past, I’ve never allowed my ammeter to go above 15mA, but since it’s controlled in the software, should I just not worry about that anymore? How do I handle the hardware bits relative to the new software? I hope that makes sense. TIA.

****Edit - or, is the software bypassing that potentiometer all together??


On most boards, the pot controls the max power that will get sent to the laser, and LightBurn is choosing a percent of that. In nearly all cases it’s best to set it to 15ma (or whatever you choose) and let the software take it from there.

The only exception is grayscale photos, where dialing down the max and using 0 to 100% in the software will give slightly better shading. PWM has a range of values. Often 8 bit on lower hardware, some are 10 bit, and as high as 14 but on DSPs.

If you’re using grayscale in the range of 0 to 5%, on 8 bit hardware that would only be about 13 unique levels. On 10 bit it’d be 50. Only on the 14 bit hardware would you have enough resolution left to get good shading within that small a range. Setting a lower power on the pot and then using a higher percentage in the software will let you use more of the PWM shading range, but the only place you’re likely to notice is if you’re doing grayscale.


Thanks…great info. Appreciate the reply.


You mentioned Mini Gerbil - it would be worth asking Paul how many bits the PWM is - I know the original Gerbil was an 8 bit board, but the STM32 that the new one is based on might be doing 10, 12, or even 16 bit PWM. If it’s the latter, you could just set & forget the pot.

1 Like

@pauldg123 would you mind answering this? Thanks!

1 Like

The Mini Gerbil board has a 32 bits processor which is doing 16 bits PWM. The legacy Gerbil has a 8 bits processor and does 16 bits PWM too. So that’s why we bypass the potmeter all together.

However there is more to it as explained above: you should dial in the black just as it hits the darkest spot (not burning through the wood), of course speed is also playing a role. The faster you go, the less time the wood has to start burning hence you need to increase that upper range with speed. I wrote a blog about this here: K40 laser best possible engravings