what PWM frequencies are usually used for lasers? I have a 12V and 2.5W (electrical) Lasermodule. My intention is to engrave grayscale pictures in wood. It works somehow but its not perfect as it seems that the optical and even the electrical power is not linear against the Duty-cycle. I also noticed some flickering at the lower Duty-cycles (below ~25%) which tells me that this might be an issue with the integrated Driver in that Lasermodule?
I have made a Test-picture with 10 Gray-scales stripes from 100% Black to 0% in order to test my settings. The best result I managed for now is PWM at 490 Hz and the Duty-cycle should be between 60% and 65% which is very narrow but for now the best result in terms of contrast. Other Values for example causing that the engraved test-picture is all black above 50% and then gets almost immediate white.
So I have three parameters to play with:
Max Duty-cycle
Min Duty-cycle
PWM Frequency
What i really want to now first is what impact does the frequency have on the optical power? Also what is usaully the process to calibrate the duty-cycle to have a nice contrast through out the whole grayscale? Do you have any extra tipps on that topic?
That looks like a BARE laser module.
Without a proper DRIVER module you may find the results erratic at best.
Also 2.5 W would be considered quite low in power and you may also find that the speed of travel needs to be adjusted for different wood characteristics.
I find that a 5W module works well for almost all woods here but occasionally I have to move up to a 10W module for some hard woods.
The power supply will also be a very important factor in terms of the current it can supply.
If the power supply cannot maintain constant current you will also get poor results.
It looks like you are also getting a non OFF state between moves which would be alleviated with a proper driver and sender program such as LASER GRBL.
I really can't tell, its from China beacuse I wanted something cheap for starters. Maybe this the main problem here.
ballscrewbob:
That looks like a BARE laser module.
Without a proper DRIVER module you may find the results erratic at best.
Also 2.5 W would be considered quite low in power and you may also find that the speed of travel needs to be adjusted for different wood characteristics.
I find that a 5W module works well for almost all woods here but occasionally I have to move up to a 10W module for some hard woods.
The power supply will also be a very important factor in terms of the current it can supply.
If the power supply cannot maintain constant current you will also get poor results.
It looks like you are also getting a non OFF state between moves which would be alleviated with a proper driver and sender program such as LASER GRBL.
The Powersupply can provide 5 Amps, this is sufficient I think. You might be right with the Power and I should look for something better than this China stuff. Do you have recommendations?
What do you mean with a non OFF State between the moves?
You can see the lines created during the moves to the next greyscale pattern.
That usually means it did not turn OFF before it moved.
Once it completes on of those patterns a NORMAL function would be for the laser to turn itself OFF.
I think it may be better if you include some links to what you purchased item by item ?
That way we can advise a little more.
The same goes for what software you are using to send the pattern and how you are generating the G-CODE to send to the laser.
The more information you give us the better we are able to respond.
ballscrewbob:
You can see the lines created during the moves to the next greyscale pattern.
That usually means it did not turn OFF before it moved.
Once it completes on of those patterns a NORMAL function would be for the laser to turn itself OFF.
I think it may be better if you include some links to what you purchased item by item ?
That way we can advise a little more.
The same goes for what software you are using to send the pattern and how you are generating the G-CODE to send to the laser.
The more information you give us the better we are able to respond.
Bob.
Oh those lines. They are because I just tested something there. Don't mind it. The code usually turns the laser off. For Safety reasons I even programmatically blocked enabling the laser when the Laser is not engraving. I made my own Code for everything and do not use much libs besides a Ringbuffer.
This is the laser I purchased, I hope its okay to post the link here: Aliexpress
Keep in Mind that the Laser I got has no top mounted PCB with the Transistor and PWM. It just has +12V and GND line.
For the Rest: I use a Mega2560 or even a Teensy4.0, some steppers from an old 3D Printer with driver and some printed parts.
The Laser is connected to a MOSFET (IRFZ44N); on Gate PWM with 10M resistor to GND. Some Caps between 12V and GND. This is the complete setup. So as mentioned in my own code I can set the PWM Freq, Dutycycle, Speed of the Axis via Interrupts...
Below are two tests I made with my default settings. And I think it could get much better than this!
Those examples don't look to bad for just starting out.
Using pictures without any edits is a truly hit and miss affair.
Quite often I will spend some time to reduce the background. LaserGRBL also has some nice controls to help with that aspect that will allow you also to reduce some of the background whilst promoting other aspects you want to keep.
I always look for aspects in pictures that will disrupt the flow of the main content and where possible remove it.
Having actually sold pieces taken as a commision it is well worth the edit time.
Doing so will also reduce the power ON time for the laser extending its life too.
Not having the driver for your laser and instead just using a MOSFET may get you by for now but do consider next time you are in the market for a laser getting one with the driver board as they make it so much easier for fine control
As far as part of your original Q. the PWM range is the same as the pwm range from whatever controller you use so either 0 to 255 or 0 to 1024.
As to what that reflects in terms of greyscale will more often depend on the material you are trying to engrave.
So where possible always do a small test sample to prevent over burn or do an initial burn at a lower setting whilst being prepared to do a second burn if needed.
The grain flow on wood can also dictate different power requirements so burning across the grain is different to burning on the end grain.
Colour also plays a key factor with power being absorbed more easily with different colours.
Surface finish also plays a key factor as a shiny surface will not burn as well as a matt finish.
Thank you for your help. So indeed I now have some strategies for improving the quality of the images and also understand that it is always very dependent on the material as well as on the lasermodule which i'm going to replace by something better as my next step
As you used Aliexpress ( my favourite place ;D ) it is worth the time and effort to throw a few lasers in your cart and weed them out just before you want to buy.
Be prepared to do a little scouting around Ali for the best prices.
Leave them in there a couple of weeks and you should find that some of them will come down in price.
![[000064]sml.jpg](https://europe1.discourse-cdn.com/arduino/original/3X/9/0/9033ff98c5115b52514e88f2d18306e296d88298.jpg)
![[000064] v2 sml.jpg](https://europe1.discourse-cdn.com/arduino/original/3X/3/1/31f1d288a9862528d1134dd6dfc1ae48818e56ba.jpg)
