Increase CNC PWM output voltage for diode laser

@Julien I ended up getting the Sculpfun S10 laser module and have wired it into the Shapeoko 3 XL. I tried putting the I/O voltage adapter to up the voltage to 12v, but got nothing out of the laser that way. I’ve got it running without the adapter, but I’m sure I’m not getting the full power out of it that I would like. Maybe I have not wired it correctly? I got the PWM + and - wired first to the I/O adapter, then the output of the I/O to the laser. Nothing happened. Once I removed the adapter, it has worked just fine. I’m not sure how else to do it. Suggestions?

Hi @Gawain,

Do you have documentation for your laser module ? you need to figure out what’s the expected input analog voltage for the laser signal. Note that this is separate from the laser POWER itself, hopefully you have a dedicated power supply that came with the module for that ?

Assuming the laser module takes a 0-12V PWM input (I have no idea without seeing the documentation, I just extrapolate from your description), you will input need a converter to bump the shapeoko’s 0-5V PWM output to a 0-12V output towards the module.

If you wired the shapeoko’s PWM directly to the module, chances are the actual output maxed out at less than half the full power than can be commanded (because you will be sending 5V max, when the module, presumably, has an input range of 0-12V so 5V would be ~40% of that.

If nothing happens when in insert the adapter in line, it must be because the adapter does not work properly. Did you get any documentation with that adapter ?
You should be able to check the output voltage with a voltmeter for a given input. Some adapters have a small potentiometer on the board that to adjust the output power, it may be set to output 0V by default. It all depends what adapter you got.

What I/O voltage adapter?

Looking at the specs here:

https://www.sculpfun3d.com/productinfo/843981.html

you need something like this:

The big thing is to make sure the I/O adapter can handle the PWM Frequency being used.

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I don’t have any useful documentation for the laser other than the PWM voltage being 12v. I have the 12V power input running on an external power supply and the PWM + and - are coming from the Carbide 3D control board. The I/O is connected directly to the PWM +/- inputs. (Before connecting it, I plugged the I/O into the 12V power supply and adjusted the potentiometer to 12v output.) The laser is then connected to the power supply and the I/O outputs. When connected this way, the laser stays on all the time and does not seem to be controlled by the PWM input at all. I said on the original post that it didn’t work at all, but forgot that it works, but is not variable at all, just continuously on.

@Gawain

As I said above you need an Logic Level converter to switch the 5V logic of the Carbide3D board to the 12V logic the laser is expecting.

With 5V logic a voltage of about 0.8V or less is considered a 0 and a voltage of about 2V or higher is considered a 1. Anything between 0.8V and 2V is considered undefined noise. The circuit can treat it either way.

With 12V logic a voltage of about 3V or lower is consider a 0 and a voltage of about 9V or higher is considered a 1. Anything between 3V and 9V is considered undefined noise. The circuit can treat it either way.

As such when you connect a 5V PWM output to a 12V PWM input, best cause it wont turn on. Worse case it could behave erratically.

This board will do that conversion for you:

It will also isolate the two circuits from one another preventing feedback noise from one to the other over the ground. You should also make sure to NOT share the ground pins between the laser and the Carbide board.

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@CthulhuLabs Thanks for the pointer and the detailed information. I’ve ordered one of those and will give it a shot. Can you clarify and explain your last sentence about sharing the grounds?

Your laser has a power supply and the Carbide3D board has a power supply. They each have their own electrical ground. These are not necessarily the same ground. If you connect them together you can create a what is called a ground loop. The board I linked to use Optocouplers to isolate the two circuits. These are basically an LED and a light sensitive diode that are optically connected but electrically isolated from each other.

Basically you connect the GND and PWM pin from the Carbide3D board to one side of the board. You then connect the 12V, GND, and PWM pins from the Laser to the other side of the board. The PWM signal from the Carbide3D board turns the LED on and off based off the PWM signal. The light sensitive diode then carries this signal to the other side without connecting the GND.

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