Hello dear Laser friends. I converted my 100W laser to a SKR 1.4 Turbo so that I can use Lightburn. Unfortunately I have a problem with the PWM signal. I have already tested some of the board’s PWM pins, they all behave in the same way. The signal fluctuates. If I now laser a rectangle of 100mm with 1% power, I get a rectangle on the wood which is brown at the ends on the left and right (felt with 15% lasered) and in the middle it was not lasered. The signal increases when the direction of the X axis changes by 0.15V, measured with a multimeter. The increase in power can also be seen on the analog mah display. At the edge of the rectangle with approx. 5 mah, in the middle with 1 mah.
I tested the following pins: 3.25 / 2.0 / 1.27
I also tested the L and H connection of the power supply for the laser fire pin. The PWM is connected to the IN connection.
I also tested the Cohesion3D firmware.
Unfortunately, I cannot use the laser like this, because I also have to laser fine details with a small font 2mm high and this is blurred.
I am about to simply reinstall the original board and then use CorelLaser which was included with the laser. Even if this program is very annoying ;-(
I know nothing about Smoothieware or SKR 1.4 Turbo but took a look around.
First off, the smoothieware documentation seems to be inconsistent. In one location it lists only pins P2.0 - P2.5 to be valid but lists 2.0 to 2.5, 1.18, 1.20, 1.21, 1.23, 1.24, 1.26, 3.25 and 3.26 in another section.
Of the ones you tried only 2.0 is in both lists, 3.25 in only one and 1.27 in none. Default seems to be 2.5. Have you tried that?
I assume these Pin numbers are from Smoothieboard. Don’t know if SKR 1.4 Turbo is an exact clone.
One thing he mentions in that site is that SKR only generates PWM at 3.3V whereas the laser required 5V. He was doing a 60W K40 conversion so your laser may be different. If you have the same issue you may not be getting the full range of modulation that you expect since it’s only driving from 0V to 3.3V for the full range of values.
I’m very surprised that you get anything out at 1%, assuming it’s not an RF excited laser… Most won’t lase below around 10%. My 50 watt lowest is about 9.4%…
I think @berainlb has given you good direction to speak with @donkjr about the HV issue on your machine.
Thank you very much for the information. I already knew a lot, I also found the French page and read it completely. I’ve already tried pin 2.5, no change.
I measured a few more values. I think I’ll buy another board.
I’ve already tried the low and high pin of the PSU, both behave in the same way. As far as I understand, the signal should be perfectly clean. However, it is not. When switching on e.g. from 3.3 to 1.2V for the high pin.
After the change of direction, Lightburn sends the controller to deactivate the laser and reactivate it immediately. This causes the PWM signal to rise briefly from 0.25 V to 0.35 V.
In my config the min Laser power is 0.006. so the range from 0-6% is not used and only then does the laser ignite. If I now work with the set 1%, the laser ignites briefly and then goes off again. And that with every change of direction of the X axis.
I also never get full power, no matter what I do, the display never goes to more than 21 mAh.
So I am assuming that this board is incompatible.
So I won’t research this any further and buy another board.
It’s a shame because I still had the SKR in the cupboard.
Which board is recommended? I’ve heard that Arduino-based boards are not recommended because they reach their limits at the high speeds.
The most common cards that I’ve seen used for upgrades would be Cohesion 3D and Mini Gerbil 2. I think these tend to be very common because they’re designed to be easy replacements in K40 lasers.
Alternatively you could buy a DSP controller like a Ruida 6442 or 6445. These are the best supported controllers on LightBurn.
You need to connect only one wire from skr’s ground of the fet you’re using to L port on the LPSU. is that how you wired it? can you share the diagram showing how you connected the SKR to LaserPSU? also share your laser section in smoothie’s config file.
