Anet A8 PWM output for fan has laser on full power all the time

Anet mainboard
Marlin firmware
PWM laser (Endurance Laser, 10W) which can handle 12v PWM.

So my issue is that when I use the PWM output for the fan on my Anet A8, the laser just stays on full power.

the laser has it’s own power supply.

I’m wondering if the Anet board is switching the ground, not the +12v? can anyone confirm? If this is the case, and I am using seperate supplies, the +12V would just be floating, so I think I am correct in saying that either the mainboard and laser need to share the same supply, or at the very least have their respective grounds tied together?

Any help would be most appreciated.



yes switching is ground side…i used on optocoupler


The thought exercise I went through was correct then. Thank you for confirming. I shall source one and go from there. Hopefully that will resolve the issue for me! Aside from this issue it seems to work great.

Thanks again!


Yes it’s working fine with a pc817 optocouler just have some minor issues which could be backlash or settings

Excellent. I’ve just ordered a 12v optocoupler to throw in to it.

The results from mine are much sharper than yours (meant in the nicest possible way)… Are your 3D prints ok? Or does it no longer have that functionality? What laser are you using?

i removed the 3d printing parts… (also meant in the nicest possible way) it was a crappy 3d printer now moved on to a much better machine for 3d prints. I am still getting the hang of board “printing” with it…getting better at every iteration but these lines are driving me insane

yesterday had one turn out fine…today we are back to random lines…i dont know whats going on and probably going to try some other software as its getting to me now

not perfect but MUCH better with flood fill mode…Bi-DIR and overscan OFF

Mine isn’t really an anet now. It uses the anet board, and the original steppers, but that’s it.

I made a stainless steel frame which improved things dramatically (but introduced other issues like higher frequency ringing), changed the slide bearings for better ones, I don’t really use the direct drive extruder any more, it’s now a boden extruder, then I made a quick-change tool system so I can swap between laser, boden extruder, direct drive extruder, flexshaft mill or dremmel wand in about minute or so. Fitted rubber stepper mounts to eliminate the ringing, belt tensioners, and various other bits like a big MOSFET for the heated bed, and now have a selection of hot ends for different jobs. I am at a point where I can say I designed and built the printer.

I’ll get some pics when I’m next at my workshop.

That’s way better. If you switched bi-direction off that definitely suggests lash. If you grab the laser can you feel any play in any direction? I remember my anet was sloppy on the Y axis until I changed the sliders.

no play at all with the steppers on

Hmm that’s interesting. I hope you find a resolution soon!

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