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Scanner opinions

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ElektroFreak

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Solonar said:
No indications of a short anywhere. grounds are connected to ground, and signal lines are isolated from ground.

Made a couple of changes, shifted the x and y cables to different lines. My breakout board has only 2 lines, and the signal cables have 3.

G x- x+ G y- y+ They were setup on x- x+ and y- y+.

I shifted the cables to G x- and G y-.


ILDA @ 20kps
100_0423.jpg


ILDA @ 6kps
100_0424.jpg


abstract type shows look ok, but anything that has a graphic or text looks horrible.

YouTube - 100_0417.MOV
Click to expand...

What kind of galvos are you using? That looks like the galvos are being run too fast.. The fact that the test pattern looks perfect at 6 degrees makes me think the problem isn't in your DAC.. It is kind of wierd that your galvos won't go over 6kpps.. Is this in Spaghetti?

Also, single-ended or differential doesn't matter much. They both work great as long as the peak to peak voltage swing is roughly the same. The only advantage differential signaling has is noise rejection and less attenuation over a long distance cable, but these days with most professional laserists going wireless it's no longer necessary. Unless you're routinely running several hundred foot long cable lines to your projector, you won't get anywhere near enough noise or attenuation to require differential signals.
 
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aXit

aXit

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Is it true that some galvos can't reach their max scan angle with the +/- 2.5V that is coming from the correction amp? So differential could be necessary?
 
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ElektroFreak

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That is true, but differential is still not necessary.. All you need is a little more juice on the op-amps of the correction amp. I recommend using a +-12V DC-DC converter as doing so will give you a roughly 9V p-p signal, which is damn close to the ILDA standard of 10V p-p.
 
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Solonar

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Yes, this is in spaghetti, but LFI shows same results.

The galvos are PT-20k's.

The good pattern was done at 6kpps and <5° scan angle(actually everything is done @ <5° scan angle).

My 12v DC-DC converter is still on back-order, but at the low angle I am using it should not be a problem. I can increase the angle, but I doubt I could even get a good pattern @ 6kpps then. According to the manufacturer the galvo's chould be able to do 20k @ 20° and 30k @5°. The galvo's themselves are really quiet when operating. I imagine they would work fine for a beam show, but don't think they will ever do graphics well.
 
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ElektroFreak

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I just bought a set of PT-20s.. haven't hooked 'em up yet though. I would recommend contacting Sam @ spacelas since it seems to me like your scanners are mistuned. I've never seen any problem with the DAC or software lead to that kind of output..

Also, have you posted about this over on photonlexicon.com? There are a bunch of great minds there that know more than I do about these things.. couldn't hurt to get their input.
 
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Solonar

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Mine came from ebay seller chinalasershop and they have not been helpful at all( They also misrepresented the scanners as 30k also). They didn't send a manual initially, and they never sent the spare mirrors(Even though they said they mailed them)

Considering these30Kpps HightSpeed Galvo System laser galvo scanner - eBay (item 180495981664 end time May-18-10 17:14:56 PDT), but I've not been able to find any feedback on them.

No, I've never posted on PL. I've gotten the impression that if your not using Pangolin that you are not worth responding to.
 
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carmangary

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It looks like your DAC is OK but I would double check that there isn't any cross talk between channels. If you don't have the Windows config right the Windows sound mixer will mix the channels a bit and you end up with distoration. It doesn't look like that is the case be be sure.

Above you said your DAC is putting out +-2.5? That's way to low. Most scanners want +-10V sent to them. You should at least be able to get +-5V out of a sound card DAC with a +-9v DC-DC regulator.

Have you messed with the pots on your scanners? It looks like they are just really badly out of tune to me.
 
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Solonar

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No, I get ~+/-5v on the scan channels, and 0-5v on the rgb channels. The 2.3 v was caused by a bad USB cable.

I've only adjusted the pots to correct some overshoot, and lower the size.
 
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Solonar

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New galvo's fresh from the box. Not even tuned yet. Also need to adjust my blanking to get rid of the trails.


100_0439.jpg
 
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ElektroFreak

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What speed is that at? Looks ok to me.. I wouldn't try to tune those galvos.
 
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Solonar

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This is what I get now. I still can't seem to get blanking correct. I may have some crosstalk issues. I plan to start changing my signal wires to shielded cables.



100_0441.jpg


Still waiting for my 405 dichro. so violet circle didn't show for some reason
100_0443.jpg


100_0444.jpg


100_0446.jpg


This has been my biggest issue, anytime multiple circles are on screen, they don't close properly.
100_0448.jpg
 
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carmangary

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The scanners look to be tuned really well. Don't worry to much about the blanking because it changes as soon as you change the image size. Best thing to do is tweak it while viewing an actual laser show. Setting the blanking to those test patterns may not give you the results you are looking for anyway.
 
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Solonar

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The last picture is from the "scooter" show, paused to show the open circles.

Otherwise, 90% of the shows I have look great.
 
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