I’ve converted my old 3D printer into a laser engraver and bought a LaserTree K20 module for this. It has the following inputs: 24V, GND, and PWM. My mainboard is a Bigtreetech SKR 1.3, and I want to run the latest Marlin version 2.1.2.5 on it.
The axis movements works like a charm with the TMC2209 drivers.
But I need some guidance with the laser control.
Since the SKR 1.3 doesn’t have a dedicated laser control pin out of the box, I planned to use a FAN PWM pin (e.g., FAN0) instead. I configured Marlin FW as best as I can and connected the fan output to the Laser tree Adapter board input as described in the manual. The power source switch on it is in the middle position for “EXT”.
My problem: I can’t control the laser whether with the LCD not with lightburn. The driver board is continuously flickering and it doesn’t react to any changes for pulse test. It doesn’t respond at all, no matter what settings I check in Marlin or how I adjust the wiring.
Has anyone worked with a setup like mine before or has an idea what I might be doing wrong? Any help would be greatly appreciated!
That shouldn’t be Make sure the head gets constant 24V on the 24V and GND pins. The PWM pin needs 0-5V pwm signal. If you have an extra power supply for the head, make sure that both power supplies share the same ground (connect those).
Yes, that’s how I understood it. But I’m also new to Lightburn and need to know how Lightburn and Marlin interacts together. Is there an option in Lightburn to choose from which pin the PWM-Signal is coming from? And is there an option to trigger the laser from the software side just for test purposes?
Edit:
This is the driver board between laser and SKR 1.3
I’ve connected the PWM to input “D”. And a flickering PWM led on the driver board means for my understanding that there is something incoming, but on the other side PWM means the laser should do something depending on the length of the signal, but it is off. After switching the driver board switch to INT as power source the laser immediately turns on with full power, so in general the laser is OK.
What I can try to test is, to setup an Arduino with a Potentiometer to test the laser standalone without the SKR Mainboard to check the general function.
No. LightBurn uses just a simple control protocol, and the firmware needs to handle all low-level stuff. It’s the same as the 3D printing gcode, just a smaller subset of it. That’s why it also speaks some parts of the Marlin dialect. It only commands “move there” and “fire laser”, and the firmware does the rest. No setting of pins is available.
Yes, that’s called the fire function, if that’s available for Marlin as well, you can turn it on in device settings and fine the button in the move window then.
Make sure the head gets constant 24V on the 24V and GND pins. The PWM pin needs 0-5V pwm signal. If you have an extra power supply for the head, make sure that both power supplies share the same ground (connect those).