hardware-level technical scanner questions (for Arduino laser beam steering project)

[Yerkat]

I'm working on a project where a laser beam has to be steered by me, not a laser show software.
The scan speed requirements are very low, as it takes input eye tracker data and moves a laser beam where a person is looking.
...basically it allows people to pop balloons by just staring at them.

Servo motors work but they make annoying noise from their gears and arent very accurate.
Since cheapo slow scanners are so cheap, why not just use them I thought. After all laser beams are what they are meant for.

Okay, so first question.

1) Is 0v the minimum tuned angle of the scanner in a given axis and 5v the max angle, or is the signal more complicated than that? For controlling I'm going to be using an Arduino taking input from a PC which in turn takes input from a webcam eye tracker camera.
2) Since the speed is so slow, is there a chance to bypass the need of large amps?
3) Since the speed is so slow, is there a chance to use 12V DC to run it rather than 24? I already use 12 for everything else so would be nice to not add an extra PSU to the box.

[JohnYayas]

ILDA signals are +-5V at the pins which actually gives you a +-10V swing.
The cheaper 12/15K scanners were single ended, though. So, one pin is always 0V and the other swings between +-5V.
Either way, 0V is center and +-5v for the extremes.

I don't know of any 12V scanner amps. The 12/15K run at less than 24v, though. I don't remember what. Maybe 15V.

I have some 12/15K scanners in a box somewhere that I probably won't ever use in case you are interested in buying them.

[Yerkat]

I see thank you, I already have a pair being send my way from Goldenstar. I will ask about voltage. There are some really small DC to DC converter boards, depends on whats the typical power consumption from these slow scanners.

Whats the resolution of these kinds of scanners? I know signal is analog, but I doubt the precision is not fix bit rate. Or am i wrong? I only need about 0.5 degree precision.

Also should special care be taken in my software for filtering the signal value before sending to the scanners?
By that I mean for example extreme jumps (-5 to 5V)? Or is that not much of an issue if the the scanners are updated only each 1/60th of a second and follow human eye rotations.

Thanks.

[absolom7691]

Whats the resolution of these kinds of scanners? I know signal is analog, but I doubt the precision is not fix bit rate. Or am i wrong? I only need about 0.5 degree precision.

To my knowledge, galvo amps are pure analog. At least, the galvo and amp setups we use for lightshow application. Some of the more esoteric setups *might* use digital amps and linear photodiode arrays in the galvo but none that I know of. Basically, galvo servo amps are a quad op-amp comparator fed to an analog output stage. The "resolution" could possibly be measured in "bits" but I doubt it. The precision or "resolution" would largely depend on the sensitivity of the photodiode in the galvo, the precision of the comparator on the amp, and the stiction of the galvo bearings. There are probably a lot more things to affect the "resolution" but that would take explanation from someone with way better galvo kung fu than me.

0.5° resolution should be no sweat at all even with cheap galvos. I would dare say 0.25° would be easy.

[Yerkat]

You are right, bit depth comes from the DAC chip, not the amps themselves.

I think a 3A DC-DC step up converter should work fine for doing 12V to 15V conversion for a 15V 15KPPS scanner, right? It apparently consumes 1A +15V and 0.5A -15V, whatever that means.

[kecked]

What happens when someone accidentally looks at a persons eyes who calls their name or ask a question or a noise startles them. I hope you put a hand trigger in this so they look and then have to pull a trigger to fire the laser.

Cool idea but could be a potential problem if the beam is always on.

maybe make an on zone where the balloons are and outside that area no beam. Ie a mask.

[Yerkat]

Of course there will be a limited zone, I don't think I could get the scanners to scan in a human 220 by 130 degree field of view + about 180 degree head rotation.

What happens when someone accidentally looks at a persons eyes who calls their name

They become the balloon.

[Yerkat]

I need to power a slow 15KPPS galvo from a 12V PSU. The original PSU is dual +-15V.
Is there anything like this but for higher currents?
https://www.ebay.com/itm/5V-6V-9V-12...Vq8DyJ_NoYGOug

Need 15volt/1A and -15volt/0.5A

[kecked]

might try two or three in parallel. should off the current needed. not really sure if you can do that with dc dc convertors. wonder if you can just add some D cells in series to up the voltage.
quick search says might work but run risk of one of the regulators be slightly higher voltage and ends up taking all the current. I like the d cell idea as it can handle the current and increase the voltage.

can you change the driver to work on 12 volts? Did you try 12v. might work fine just a touch slower response.

[Yerkat]

rotation speed is not important but response should be instant