PWM Laser

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Bradley25
Posts: 5
Joined: Fri Jan 03, 2020 7:01 am

PWM Laser

Post by Bradley25 » Fri Feb 14, 2020 6:49 pm

I just bought a laser that has no information with it. I have it hooked up and can turn laser on and off. But it doesn't seem like the intensity is changing. Also in one of your post you said you changed the duty cycle and a couple other things. What kinds of things did you change?

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Doug
Posts: 154
Joined: Fri Feb 02, 2018 4:56 pm

Re: PWM Laser

Post by Doug » Sat Feb 15, 2020 6:24 pm

The laser is configured by selecting PWM Spindle on the "Tool" page. Here are some starting settings:

tool-reversed: unchecked
max-spin: I use 255, but the main thing is that this needs to be the same as the maximum value that will be assigned by your CAD/CAM system. This is given with an S Command in GCode.
min-spin: 0
tool-enable-mode: doesn't matter, you probably won't use the tool enable output from the BB Controller
tool-direction-mode: doesn't matter, you probably won't use the tool direction output from the BB Controller
pwm-inverted: probably unchecked, but this depends on what the laser pwm input expects
pwm-min-duty: 0%
pwm-max-duty: 100%
pwm-freq: 1000
rapid-auto-off: checked, This will cause the laser to automatically turn off during rapid moves (G0's). It also causes the controller to turn moves where the laser is off into rapids.
dynamic-power: checked, This causes the laser power to be adjusted during periods of acceleration and deceleration preventing overexposure that would otherwise occur.

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Doug
Posts: 154
Joined: Fri Feb 02, 2018 4:56 pm

Re: PWM Laser

Post by Doug » Sat Feb 15, 2020 6:34 pm

Another issue that some people have encountered when hooking up lasers to the PWM output on the BB Controller is incompatibility of voltage levels. The BB Controller PWM signal is 0 to 3.3 Volts. Many lasers that use PWM inputs require 0 to 5Volt inputs.

If your laser does not work with the BB Controller, consider purchasing a 3.3V to 5V level shifter like the one found here: https://www.sparkfun.com/products/12009

Bradley25
Posts: 5
Joined: Fri Jan 03, 2020 7:01 am

Re: PWM Laser

Post by Bradley25 » Mon Feb 17, 2020 12:43 pm

I have purchased Logic level Converter. I will let you know what happens when I get it hooked up.

Bradley25
Posts: 5
Joined: Fri Jan 03, 2020 7:01 am

Re: PWM Laser

Post by Bradley25 » Sun Feb 23, 2020 11:07 am

So hooked up my Level logic converter and laser just turned on full. After some testing I can disconnect the power from the BB controller to the Logic Level Converter. I could actually turn on and off the laser. And control the power. Just not full power. I wish this laser had some more info.

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Doug
Posts: 154
Joined: Fri Feb 02, 2018 4:56 pm

Re: PWM Laser

Post by Doug » Mon Feb 24, 2020 1:33 pm

How can you tell whether the laser is putting out full power?

Bradley25
Posts: 5
Joined: Fri Jan 03, 2020 7:01 am

Re: PWM Laser

Post by Bradley25 » Tue Feb 25, 2020 8:28 am

Honestly I don't.

I did read that it should work with TTL voltage from 0-12v. If that is true I have no idea. But when you put 12V to the PWM line it turn on instantly starts burning a hole in stuff. I am going to get the scope out and see what is going on. Thought I could pull this off with just a meter but it isn't looking that way. I will see what I can do.

Bradley25
Posts: 5
Joined: Fri Jan 03, 2020 7:01 am

Re: PWM Laser

Post by Bradley25 » Mon Mar 02, 2020 1:00 pm

I have fixed the Laser problem. Turns out when we switched it to be inverted that was causing a problem with the whole setup. I put the O-scope on it and see how it was inverted. So when I was asking for full power it was basically shutting off. After adding logic level converter and going back on the inverted change that I made it started working perfectly. Thank you Doug for all your help.

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Doug
Posts: 154
Joined: Fri Feb 02, 2018 4:56 pm

Re: PWM Laser

Post by Doug » Mon Mar 02, 2020 4:39 pm

Glad to help.

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