Laser Tube Fires as AC power is turned on to the machine

Guys
I’m just setting up my mirrors to get the machine up and running, and something peculiar is happening which I’ve never noticed before;
As soon as I turn on the AC power for the machine, the laser tube fires for 3-4 second or so then stops.
Ruida RDC6445G
90w Glass tube
I can pulse fire the laser from the controller, and nothing looks out of place and not sure whats causing this brief firing of the laser.
Tried it with and without LB running makes no difference
Has anyone come across this before?

Hi @Nova_Star this has nothing to do with LightBurn.
Did you move any wiring around inside your machine? Did you accidentally or purposefully remove any of the green connections between your Ruida controller and your high voltage power supply PSU?

From what you describe it sounds like there is either some electrical noise/power surge when you switch your machine on causing the laser to fire or your have a wiring issue (i.e. its wired wrongly and unless you did it, then please don’t assume this to be the case and start rewiring) where the signal from your controller to your PSU fires your laser.

Do you have high current items plugged into the back of your machine that start when you switch the laser cutter on, such as an extractor fan, air assistance and water chiller?

You mention you are “setting up mirrors” to get up-and-running? Where did the cutter come from and have you had need to make electrical adjustments?

Hi Dominic
The controller and tube came from my Chinese 6090 90w machine.
I salvaged the controller and tube and built a new frame with new steppers etc.
Wiring is as per schematics, with the addition of an EMI filter upstream from everything. The old machine (setup) from the factory had a laser ON/OFF switch which is now not connected, because I forgot to make a note of where it was wired. However I am certain it was not switching the AC side of the LPS.
So currently I only have the Rudia, stepper drivers, and LPS running. The laser functions normally after the initial 3-4 second firing when power is applied to the machine. I can pulse, I can run the laser via LB and everything seems correct.
I have gone over the wiring from ruida to the LPS double and triple checked (they are correct)
It was a complete re-wire …
Sorry, and yes I have added an air assist solenoid, but I added a RC subber across the coil of the solenoid

Since you wired it, I would double check how it’s wired. I highly doubt it’s an emf issue since it’s on power up when everything is waking up and inherently unstable. Don’t make the mistake of ‘rewiring’ stuff, that commonly induces more errors. Double checking is fine, hope you used different color wires, that’s helpful.


Never tried to turn them both on then plug it in… never dawned on me to try it… I’m fairly certain that this isn’t proper operation.

That is exactly how my lps is wired. The switch turns on/off the mains supply.

Could this have been happening since you built it?


There are only two signal wires (and ground) that are needed to control the lps.

Ruida lps
L-On1 → L - this fires the laser when L goes low
LPWM1 → IN - this could also be the analog output of the controller.
Ground → Ground

Most don’t use P which is the water protection and needs to be low for it to fire. Mine is wired to ground.

If possible put a voltmeter on the L-On1 or L and see if it goes low when you power it up…

Generally a diode is used to snuff the back emf from a coil on a relay… I have the air assist and I don’t use anything as do some others I’ve met… :crazy_face:


How is the ‘pot’ wired up?

:smile_cat:

Feel like a dumbass!!
wires labeled correctly, but I had swapped TL & IN at the LPS
Looked at it so many times but couldn’t see it
Thanks for your help people :joy: really appreciate it

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