This is all you need for upgrade your Anycubic I3 Mega to laser engraver. I use 5W laser
Electric circuit description:
SV1-1 and SV1-2 are connectors for signal from hotend fan.
SV1-3 is for 12V from power suply-
SV1-4 is output
SV1-5 is GND.
This circuit is here for converting 12V PWM signal from hotend fan to 5V PWM for laser driving board. And as a bonus I added switch, so I can easy switch between 3D printer and laser.
I added also a laser box. This is useful when you do not need the laser or when you need to carry it somewhere