Controller to CO2 laser PSU distance

Does the laser PSU need to be close to the (Ruida) control unit or is having a couple of metres of cabling between them ok? I’m thinking laser PSU within the machine and control unit in separate enclosure along with the other PSU’s and controls. Many thanks.

Almost certainly a Bad Idea™, because the signaling is basically open-collector drivers and high-impedance pullups over unterminated / unbalanced lines. A generous length of wire will introduce enough stray capacitance to affect the rise and fall times, which will in turn affect the timing.

The PWM signal controlling the laser intensity runs at 20 kHz with harmonics well above 100 kHz to keep the waveform square.

The stepper motor control signals have tighter constraints. My OMTech 60 W ticks along at 12 µm/step, so moving at 500 mm/s requires 42 kHz step pulses, again with harmonics well up above 100 kHz. On the other side, you do not want to run the stepper driver’s motor winding current through a few meters of wire: the driver and the motor must be close together.

It’s not RF, but it’s not near enough to DC to ignore the gotchas.

Bundling all those pulses in the same looong cable is pretty much a textbook description of how to generate crosstalk, too.

I’d expect the thing to come heartbreakingly close to working, with intermittent and hard-to-diagnose motion problems. Verifying signal integrity with an oscilloscope would be a Good Idea™ before declaring victory.

Thanks so much for the comprehensive reply, very much appreciated. I’ll locate the PSU and controller closer together.

Is there some purpose in seperating them?


I have a 1610 machine. The bay in middle-back where the Ruida goes is too far for the cable to reach from the front corner where the panel goes.

I just made an extension cable, it was only like 4-6 wires.

Yes, it worked fine with an extra 2-3 ft over the Ruida’s normal cable length

This is the Ruida to machine console?


Ruida motherboard to the Ruida panel. Stock cable was too short.