Hi,
I have been playing a lot with engraving lately and have seem some excellent work here. Most of the best images are with low power lasers at low speeds. I have gotten good results with dithering but gray scale has been more difficult ( 3D relief is OK ).
What I think my limitations are,
90W laser tube
Integration time of PWM input to analog control voltage in LPSU
response time of CO2 laser tube
My LPSU is a Z80 which can take an analog or PWM input. I’m pretty sure it just integrates the PWM to an analog voltage either through a passive RC filter or possibly an active circuit. I haven’t determined how fast I think it can go yet.
From dithered engravings, I think I can go about 50mm/S and support 500DPI and get good detail.
At 50mm/S my max power is about 18% before I’m carving depending on the wood.
Once running, my laser can go down to about 8-9% and still be on. For gray scale, this leaves an 8% to 18% range. When I try that, there is not much shading going on, seems like an image is really only 2 or 3 shades.
So, my idea. The PWM is 0-5V. I looked at the PWM output on a scope and the duty cyle is pretty responsive. I was thinking about putting a switchable voltage divider on the output to make it be 0 - 1.25 volts or so. That would let me expand the power to be 8% to 99% and have around 25W max for gray scale.
The idea behind this is to expand the PWM, bigger PWM pulse changes to control the output voltage
What do you think?
Joel