Change acceleration setting c3d laser board

80w china blue

c3d laserboard

Smoothie and GRBL-LPC

Machine works fine with Smoothie (*almost) but acceleration is too high and changing it in lightburn 9.07 does nothing. Tried connecting with GRBL-LPC and could home laser and move laser head (that is all I tried) but could not read config files to see/change settings. Tried placing SD card directly into three different computers to edit config numbers but no computer will “see” the SD card.
I suck as this kind of stuff, so be gentle and instruct as if I now little about firmware. :slight_smile:

*almost - can not get over 15ma through 80 watt reci laser even on 100% power. Laser actually fires when set to less than 1%. This is a brand new board, brand new tube and brand new power supply. Old board/tube/power supply would not fire unless power was around 6%. I assume this is an issue with the new power supply. Not sure if there will be enough control in the lower power settings to do nice grey scale engraving.

I should mention I am using Windows 10 on all 3 computers.

More details below. What is the normal wait time for a reply? It has been 48 hours.

when testing a job on grbl-lpc head stops and job freezes indefinitely when laser is supposed to fire
when testing on standard grbl laser does nor fire but heads moves as it should until job is finished
smoothie still works fine but acceleration is too high, homing is slow, no home offset etc.

tried to use universal gcode sender to change machine settings (used it successfully in the past) and chose GRBL as firmware but when I connect the error below appears. I have put hours into this and hit nothing but dead ends.
**** Connected to COM7 @ 115200 baud ****
ALARM: Abort during cycle

I would recommend running Smoothie, not GRBL-LPC - since we fixed the raster speed issue in Smoothie some time ago there is almost no reason remaining to run GRBL-LPC on the LaserBoard.

The SD Card was fine when it shipped from here as I am personally putting the Smoothie firmware and config files on each one. If no computers see it, you may need to get another one and reflash with clean files as explained on the bottom here: Cohesion3D Board Indicator Status LEDs

To change the acceleration and other board values, you do actually have to modify them on the config.txt file on the memory card. Changing them “in LightBurn” only changes the simulator parameters.

Also of interest, how are you “changing” between Smoothie and GRBL firmware if no computer will “see” the memory card?

I was only trying GRBL to see if I could change the accelerations. Well I just tried another computer and it sees the card. Tried two of the others again and one will not see any cards, the other sees some cards (all if I push them upwards a little bit) What are the odds?
I have adjusted all settings but have not figured how to set x/y home offset yet. Please advise.

My power settings are still funny. I can engrave at 60mm/s at 0.6% power. At full power I am still only getting 15-16ma. I had the same max power with the M2 board I had temporarily installed while waiting for the new C3D board. Anyone have any suggestions?


I took my power supply apart and fount 3 potentiometers. I was confident one of them was for the max power output and now can crank the power up to 26ma. I am hesitant to move the other two potentiometers. Tried greyscale engraving and regardless of min/max power settings in Lightburn I am essentially getting only two amounts of burn per image. I have to turn the low power down to 0.5 or white areas are still getting burned. Any portions of the image that are not pure white come out pretty much all the same color, no matter if I set the max power to 2%, 4% 10%…or up to 100%. I realize this is probably an issue for the PSU manufacturer (Cloudray) to help with but thought I would update, especially since they have been incapable of understanding and dealing with previous issues I have approached them with.

Any suggestion on above and on getting the home offset adjusted are appreciated!

There are several active topics on this form that will be answered in short with “grayscale is hard” and “laser power output isn’t linear”

On top of that, you have an 80w machine which can be more “howitzer” than “needle” when it comes to operating at lower powers.

Please provide pictures of your board, machine, and wiring so that I can see what we are working with and advise accordingly.

Home offset? Do you mean the accelerations you asked about before or am I missing something else?

My previous tube and power supply produced excellent greyscale with your mini board at extensive and various powers I am familiar with how to succeed with greyscale and 3d engraving. Perhaps the new tube/combo won’t do it? With the old equipment I could produce a pattern with 16 gradients from white to black and there were noticeable color differences between most of the 16 shades. I just burned the same image on the same piece of 3mm Baltic Birch at a multitude of power settings and there is clearly a gradient in the depth of cut, but strangely there is no real color gradient. Perhaps this offers a clue? Based on the reading I have done it is not normal for the laser to fire at less than 5-8% power. Since mine is firing at 0.6% power I am inclined to hope there is room for adjustment. Since I am getting a nice range in depth of cut when rastering do you still see a need for pictures of the wiring etc?

By “home offset” I am looking to program the laser head to automatically move a specific number of millimeters off of the limit switches after homing. It can be done manually but I prefer it to be automatic as it was with my C3D mini and M2 nano boards. My material does not go all the way to the 0,0 position of the limit switches. You also can not use over-scanning without hitting the limit switches unless the head is moved off of 0.0 before staring a job.

Thanks again for your time Ray.

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