K40 laser with smoothieware

I have a k40 that I upgraded with cohesion3d board. It homes when I start lb and shows connected. I have set it with the right comm port, and smoothie ware. I run a test with a square, and it seems to be moving ok. Except the laser doesn’t fire. If I press the test fire button on the control panel of the laser it doesn’t work either. However, if I press the button located on the power supply near the connector, the laser fires ok. Any idea what could be wrong?
Thanks in advance!

The ‘test’ button overrides all the protection signals. I would read this as a problem between your controller and lps.

I have a China Blue and I know the K40 lps are a little different, but the description indicates the controller isn’t wired/configured correctly to allow the lps to fire.

My lps has an L input, which is a laser enable and must be low. Many also have an H input for a high laser enable.

The lps have a water protect or P input, that is usually grounded also. Mine is ‘wired’ low, some are wired to the water protect switch.

The final one needed is the IN which is where the pwm control is.

The test button overrides all of these, so it seems to indicate one or more of them are not operating properly. It might be a controller board configuration for these signals…

Don’t know if this is helpful…


Thanks Jack. This what I thought as well. I checked the laser enable with an ohmmeter and with lid close resistance is 0. Opening the lid show infinite R

That’s one of the three…?


One of the three? The middle connector, the two left position is enable. As I said closing the lid will short this then enabling laser (or suppose to) you referred to test button, the one on the lps or the one on control panel?

Anything going through the controller will retain the safeties (protections) that the machine uses. The ‘test’ button on the lps will fire the laser, no matter what state the safeties are in.

The three required are the L, P and the pwm.

Your response was for P, what about L or the K40 equivalent.? Hence 1 out of three.

Do you have some kind of water protect to ensure the machine has coolant flowing.?

On the Ruida, all the sensors go to the controller, it then applies these to en/disable the lps. Same end solution, just a different way.


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