Laser Diode on the 126

[daregone]

Hoping to get a little help here.

I have a 2 watt laser diode that has 3 wires. It runs off 12v (Black,Red) and has a control line (white). When the white line is grounded - the laser is off. When the white is high, the laser on.   I would like to control the diode with PWM if possible, but would be happy to just to get it reliably turn off and on at the beginning of a cut.

 I am using a pdmx-126 to run my cnc router.  It has a smoothstepper (ethernet) and superPID to control the speed of the router- all running under Mach3.   My preference would be to NOT have to disconnect a but of stuff, but rather to able to switch between the router and the laser through Mach.

My problem seems to be with how things are grounded.  To test the things, I was attempting to control by toggling pp16 located in J6.  I assume everything in J6 is grounded relative to pcGrd.   The idea was to use one of the of unregulated unregulated +12v on the board.  However, they are on a different ground (not pcGrnd) . The documentation says not to tie pcGrnd to any of the other grounds on the board as it could cause a ground loop.

Any help would be greatly appreciated.

[Steve Stallings]

You are correct. The outputs on J6 are referenced to PCgnd.

There is an unregulated +V output on J7 that is near 12 volts and
referenced to PCgnd,  BUT neither it or the +12U on J11 and J12
are capable of anywhere near the amount of current needed to
operate a 2 watt laser diode. You will need a separate power
supply. I would recommend using an isolated regulated 12 volt
supply and tie its negative to PCgnd so that the laser diode
driver will see the logic level outputs on J6. Your laser ground
will be connected to PCgnd and not connected to GND (machine
side ground) so there is no cross connection or ground loop.

This still does not address the issues of Mach3 configuration
swapping and how to provide control of the laser that is properly
synchronized with motion. The latter is plug-in specific, so I would
recommend that you consult with SmoothStepper experts on that.

[daregone]

Thanks!  That is what i needed to know. 

I am still working may way up the learning curve on this.  It is my understanding the smoothstepper can automatically adjust the pwm output to correspond to changes in speed of travel.