I need help to build a test rig for a laser

Hi All,

I have a very old 25W CO2 Laser that has been handy for marking and cutting stuff. The win-3.11 software to run it via the parallel printer port is toast so I set about reinstalling it on the old PC. Unfortunately one of the three win-3.11 diskettes is no longer readable. Time to update the software. The laser has it’s own HF supply internally so all it needs is the tickle pulse and then vary the PWM for intensity.

From the manual.

Control (CTRL) Input
Logic Low (Off State) … 0.0 V to +0.5 VDC; 0.0 V nominal
Logic High (On State)… +3.5 V to +10.0 VDC; +5.0 V nominal
Maximum Current Load… 6 mA @ +5.0 VDC
Tickle Pulse Signal
Tickle Frequency 5 … 5 kHz
Pulse Length… 1.0 μs ± 0.2 μs
Pulse Rise/Fall Time… < 100 ns between +0.5 V to +3.5 VDC
PWM Command Input Signal
PWM Frequency 6 … DC to 20 kHz
PWM Duty Cycle … 0% to 100%

I am afraid all of that is well above my skill level here, but given that it draws 6mA, it appears I could drive this directly with an Arduino Port. So, I’d like to make a test rig with a potentiometer to test if it is indeed that simple to vary the output. If so, then I can look at a RAMPS, GRBL or Marlin solution to bring it back to life again.

What hardware and Arduino code do I need to put together a tester?

There are parallel port boards for your current PC.


Yes. You should be able to directly connect the Arduino and PWM should work. You can try the [u]Fade Example[/u].

If that works you can [u]map()[/u] the 10-bit (0-1023) [u]potiometer reading[/u] to 8-bit PWM (0-255)

I don't really understand "trickle" but you might need to make a separate function/loop to generate the trickle signal when PWM is zero.

There are parallel port boards for your current PC.

Thanks, but the Laser operates with a bespoke printer driver under win3.11. There is nothing wrong with the old PC Centronics port. But, I can no longer send stuff to the laser as win-3.11 is corrupted.

I need to test the PWM of the Laser to see if I can use RAMPS+Marlin or similar.

There are parallel port boards for your current PC.

And Win 3.11 can also be downloaded.

And Win 3.11 can also be downloaded.

Thanks, but that does not look like a msoft site to me and as well meaning as they may be ...

One never knows what one may be getting as well with unverified downloads. Besides, if I can use RAMPS and modern software, life will be a lot easier. Corel v5 and win 3.11 were not at the pointy end of ease of use.

I remember back in the day when the calculator in win 3.11 would show zero when you subtracted 3.1 from 3.11.