Lightburn does not turn on the Laser

Hello together,

I have build my own Laser machine with an Arduino Mega 2560 R3 on board.
I downloaded the grbl 1.1 with laser-mode and I customized the cpu_map.h and the config.h and the default.h.
It´s able to drive in X, Y, Z directions with Lightburn, but the laser won´t get a PWM signal.

Please can anybody help me?

Thank you in advance,
cpu_map Wolfgang.txt (8,7 KB)
config Wolfgang.txt (44,3 KB)

Your CPU map is showing the following:

  #define SPINDLE_PWM_MAX_VALUE     1024.0 // Translates to about 1.9 kHz PWM frequency at 1/8 prescaler
    #define SPINDLE_PWM_MIN_VALUE   1   // Must be greater than zero.

The PWM frequency can vary quite a bit between laser module manufacturers. Which laser module are you using? Is the intent to send TTL level signal? Some modules use pulsed 12V and ground.

A low power single-color LED with a current limiting resistor might be a good troubleshooting tool for finding your PWM pin. It would indicate for any of the frequencies selected for 6 (digital pin 9)

of interest, you may have selected the same limit pin for X_LIMIT_BIT and Z_LIMIT_BIT

  #define X_LIMIT_BIT     10 // MEGA2560 Pin D13
  #define Y_LIMIT_BIT     4 // MEGA2560 Pin 10
//  #define Z_LIMIT_BIT     6 // MEGA2560 Pin D12  TEilt sich den Pin mit Endschalter X
  #define Z_LIMIT_BIT     10 // MEGA2560 Pin D13

I assume this needs to be compiled since you changed the header file?


1 Like

Hello John,

thank you for your answer.
I use the K30 Laser from Laser Tree.
K30 Laser Tree parameters

I use a oscilliscope to be sure that I have the correct PWM pin. With ESTLCAM I have a PWM signal with ca. 1KHz and it works fine.

Yes in my machine the limit switches for X and Z are in serial and have the same pin on the board. (That´s my next issue which I have not solution).


Hello Jack,

thank you for your answer.
Yes of course. After I change something in the header files I compile and flash them with the Arduino IDE.


I’m not familiar with ESTLCAM but I’ll call on our subject matter expert if I need to.

Is there a Console window or G-code exporter that allows you to save (or copy/paste) the GCode out of ESTLCAM for Review?

If we were to compare the first 10 lines of each GCode instruction set I’m fairly confident that we’d see a difference in the configuration of the GCode sender…

In LightBurn click File, click Save GCode and save the file somewhere convenient. Please do the same with the ESTLCAM GCode. Open a new text file and copy the first 10 Lines from each of those files into a new text file.

Please upload the text file here for review and comment.

Hi John,

yesterday I did an other try:

I took an other brand-new Arduino Mega 2560 R3 and I downloaded from Github the untouched version of GRBL 1.1, especially for this controller.
I flashed the controller and took my oscilloscope and I also couldn´t see either a PWM signal on the related pin or the spindle- enable signal. nothing.

Conclusio → the problem is not Lightburn. The problem is GRBL with Arduino Mega 2560


I suspect the pin is present and just lost in the shuffle.

Do you have a link to the Source code and Binary?

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