[gnea/grbl Issue#735] Question: Using laser with 3.3V PWM

#1 – PicEngraver 于 2019-10-03

I believe an answer to your question lies entirely with the laser driver you are using. Lasers are current-driven devices, not voltage. So if the max input to your driver is designed, or adjustable, to be a 3.3 volt PWM signal to get the max current out to the laser, then all should be good.

#2 – cnburke 于 2019-10-03

Yes, the driver is designed to accept a 3.3V 20kHz PWM signal. My only concern was with the 5V output of the spindle/laser PWM pin. I may have to use a level shifter to get it to work, but I think it will.

#3 – bdurbrow 于 2019-10-05

You need a level shifter; but it can be as simple as a voltage divider made from a couple of resistors.

#4 – cnburke 于 2019-10-14

#edit – I’ve spoke too soon. Apologies for the confusion. I’ve found my rookie mistake.

Thanks! I went ahead with the proposed level shifter that @bdurbrow suggested, and that looks great!

The only point I’ve been trying to figure out now is the PWM frequency. I’ve tried changing the pre-scalar in the cpu_map.h file, but I haven’t seen any results. Any suggestion? I’m using a scope to verify the output of the signal.