Controlling 20 kpps galvos

[pnak0tic]

Hi, I have just received a 20 kpps Galvo set I bought from ebay
20Kpps HightSpeed galvo scanner (max35Kpps) | eBay

Thing is, I have figured out how to plug everything but I am a bit at loss as to how to control it (And the pdf leaflet that comes with it is no help at all)

I know I need a soundcard DAC for the signal and I already have an external soundcard (with only a single output though), but I don't know what sort of signal I should be outputing

My final application is not related to light shows so I probably won't be using softwares such as LFI player in the end but I would use such software at least to begin with so I can tune my galvos with the ILDA test pattern

So far I have been quite unsure of what to plug where as to the control signal and what to output, so any help would be greatly appreciated


From what I got by reading manuals of various systems, the input seems to be simply a DC voltage that tells the driver what angular position to get (I figure the driver then turns it into a PWM signal that feeds the galvo itself), thing is the input cable has 3 pins, IN+ IN- and G

I'm pretty sure G is ground and IN+ is probably my signal but what is IN-, the same signal but inverted? that would seem a bit weird


Thanks in advance

[flecom]

yes its a balanced signal, so you have a + and - signal, along with ground

you might try looking on the laserboy forum, they have a lot of info related to sound card interfacing for laser use

[pnak0tic]

Is it really just a DC voltage or is it some sort of pulse modulated signal or something? Because right now I am sending it varying voltages with a DC generator and I don't see any movement. Maybe the current is not sufficient, I don't know.

EDIT: Nevermind it moves! It's just that the movement was so slight that I didn't notice it

[mixedgas]

Amplify the signal with a light beam on the mirror. The light will deflect at 2X the mechanical angle because of the mirror. It is a differential aka (two wire + ground) signal on the input, so ground the - input for each axis, ground the ground terminal, and use the remaining input. There is no PWM anywhere in the system, it is a 100% analog PID loop.

The inputs only draw nanoamps at DC, so there is no need for current flow at the inputs.

Since it is the single ended input configuration you are using, you will need +/- TEN volts or so for full scale rather then +/-5V differential that the ILDA type input uses.

PS, Galvos DO NOT like PWM position signals unless they are low pass filtered to a DC average voltage, they try to follow the raw pulses.


Wiki is here.

http://www.google.com/url?sa=t&rct=j...yj_IrRD7QRqMCw


Steve

[pnak0tic]

I sent my galvo drivers relatively low frequency sine waves between -5 and 5V and was able to get nice circles / lissajous patterns

Then I unplugged my circuit. A few minutes later I replugged it to show it to someone and the X mirror started making a lot of noise and moving erratically to random positions or just getting stuck

And now it smells like chlorine all over the place

Am I screwed? What did I do wrong :P

EDIT: Also, the X driver (corresponding to the galvo that seemingly failed) got considerably hotter than the other driver that was receiving similar input

Also, pictures of my setup coming soon