gShield V5, GRBL 1.1f and a new laser not working

Hello All,
I have an older DIY cnc/laser that works with the old laser I bought years ago. but that laser now has low power output. So I purchased a new laser from Amazon to replace it thinking the PWM TTL would be just fine. Not sure if this is the issue or not.
So Here are the details:
Arduino UNO running GRBL v1.1f
new laser:
With the old laser installed, everything works normally M3 on/ M% off , laser acts as you would expect it to…
With the new laser installed, PWR / GND connected, PWM and GND connected… the laser does not turn on with the M3 command not sure I understand the differences of old laser to new laser… If can provide anything else to help you help me, just let me know.

Did I understand correctly, that this is a diode module mounted on a CNC machine?


  • Model #/manuf or old laser module
  • Wiring diagram for old laser module to controller
  • Wiring diagram for new laser module to the controller
  • What power supply is used for the laser module?

Is this the right controller?

Things to check on the laser module with DVM.

  • 12V to the laser module
  • PWM voltage at various power settings
  • Does your new module (2.5A) draw the same current as the old one?
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Don, thanks for your reply…
Let me give you what I can here…
Yes you are correct on the gShield cnc/laser machine controller
original laser

wired as TTL to pin 11 of Arduino/gShield and GND to GND
power supply is a 12V 50A linear I had laying around… and is fully working.

I am not at the machine at the moment… but will measure the PWM voltage output a little later tonight.

The new laser module is a diode laser yes… and is wired the same as the original… PWM to pin 11 of gSHield/arduino and GND to GND

Not to muddy the water, but I also have this diode laser module, and it does not work with the setup for my original laser either…
makes me think it is just a setup change or pwm voltage level issue… but the new one say it is TTL compatible…

just for reference, I have one of these also… and it does not fire the laser either.

sorry I forgot this from the previous post…
I am starting to wonder if it might be Frequency related… but not sure…

Well, i hate to admit it… but the problem turned out to be a bad connector… with the original laser, it made contact…but with the new laser, the pins were just shy of making contact… i should have caught this…

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