galvos vibrating!

Hi everybody,

I Have a 30k scanner from spaceLas :
30k high speed scanner system Max 50kpps galvo system ILDA30kpps, Max 50kpps [PT-30K] - $179.99 : SpaceLas Co., Ltd.|Laser light|Laser diode|Scanner system|Software, online shop

The problem is when I connect my Y signal the corresponding galvo starts to vibrate, it stops when I disconnect the signal .The vibration starts from a certain value of the size pot and grows in function, before this value the mirror doesn't move .

Have you any idea about this situation ?

Thank you so much for your help

(Actually I can say anything about the X Galvo because I have some wires disconnected and cannot reconise the correspondence between them)

Size pot? Where? Please tell me you're not messing with the pots on those amps without knowing what they do. That's a good way to blow them up.

You can find details in this pdf

The other Pots are pre adjusted and I didn't make any modification.

Thanks

I would check your signal source to ensure it is outputting a flat-line 0V when you're not outputting anything. That pot you're adjusting might just be amplifying input noise.

Bionic-Badger said:

I would check your signal source to ensure it is outputting a flat-line 0V when you're not outputting anything. That pot you're adjusting might just be amplifying input noise.

Click to expand...

It's connected to a DAC output channel so I have always a constant value of 2.2v in input (vref)

I'd just adjust the size pot until there aren't any "vibrations" (oscillations/overshoots) then. The size pot probably affects the proportional gain of the system, and too much can lead to instability.

Bionic-Badger said:

I'd just adjust the size pot until there aren't any "vibrations" (oscillations/overshoots) then. The size pot probably affects the proportional gain of the system, and too much can lead to instability.

Click to expand...

ok, thank you for the test

I tried also an open loop test, I mean disconnecting the two pins of the position detector PDA and PDB and see just what my driver gives in its output without having a feedback from the galvo.

The input signal is referenced at 2v(the reference voltage of the sound card) and has a maximum value of 4v.
the result is a mirror waveform of the input signal with a voltage reference of 9V the maximum value depend on the size pot and can go until 19v.
the signal output is the same with the other driver but the voltage reference is 12v.

Are this results making any sense? do you think this voltage averages are normal ?

I don't mess with the P(I)D amplifier of the galvos. They all seem to have the same design and the same chips as the ELM galvo servo amp anyway. It shouldn't matter what the reference is on the two galvo axises anyway, as they're meant to be independent.

Maybe pass your input signal through a correction amplifier to ensure that it is utilizing the full range of your galvo.