How to tune your scanners

[laserLips]

Hi Graham,

The best way to adjust the scan angle is in the projection zones window. Adjust the size in the geometric correction bit.

Dave

Thanks Dave, will have a go when I can stop playing with beams

[norty303]

Hi

I've got 2 projectors which, whilst supposedly the same appear to be fitted with slightly different scanning hardware, probably due to them being purchased 6 months apart. On looking inside I can see that one has what looks to be the SCANECO10 set that Lasershowparts sells

http://www.lasershowparts.com/files/.../SCANECO10.pdf

The other has what i assume to be the SCANECO15 set which doesn't appear on the Lasershowparts site anymore (replaced by the 20), but it has a single driver board and is obviously quicker than the other one

I had a go at re-tuning my scanners as they obviously seemed like they could do better, with noticeable overshoot, and curvy lines.

However, as you can see from the manual, they only have 3 adjustment pots per scanner, size, gain and damping. Does anyone have any idea how the damping works with these? Is it purely HF, with no LF available, and how might you go about tuning them, given that the 'stool' is now missing a leg?

Does the man at the back get the day off, and everyone else a little wetter?

[buffo]

Actually, the pot is probably LF damping, and there is no HF damping. So yeah, the guy in the back (the HF damping dude) called in sick that day, so the stool will go up the steps a little crooked, and maybe a little water gets spilled!

Bill Benner actually advocates removing the HF damping control on some scanners, simply because it makes them so much easier to tune. True, you might loose a little bit of image quality, but truthfully the HF damping doesn't do a whole lot. The LF damping is the key control, especially for scan speeds below 30Kpps.

In fact, when you are tuning a set of 30K scanners you don't have to start messing around with HF damping until you get the gain up really high. Also, it's more important to have it when you're tuning to really fast scan speeds (30Kpps or faster) than if you're only trying to get 10K or even 15K performance.

Since your scanners are rated for these slower speeds, you probably won't even notice the difference. Set your scan speed at 10K (or 15K, if that's what they're rated at) and tune them up. If you start to get undershoot on the pattern, you'll have to live with it. (Might want to tweak the damping so you have a balance between under and overshoot.)

Adam

[norty303]

Thanks for that, I'm going to wait until my FB3 arrives before having another attempt at it as my Alphalite doesn't tell you what speed you're actually running at. If i attempt to tune for 12k then I should get a happy medium between the 2 sets if i'm lucky. The slower set was getting the classic curly tails on the ends of the lines so some playing with LF will probably help.

[buffo]

Hmmm... If you are going to run both sets off the same controller, then I'd tune them both to 10K, unless you're sure that the 10K units will run at 12K...

Also, my tuning tutorial is designed to maximize the scan angle while keeping the pattern looking good. In your case though, the 15K units will probably end up scanning wider than your 10K units if you set them both to the same speed and tune them there. So you may end up needing to adjust the signal input gain (note: not servo gain!) on one set of amps so that you get roughly the same pattern size for both galvos.

Adam

[norty303]

The first thing i did was to align the 2 heads against my width markers (read: door frame!) so that they both hit the same width at the same speed of scan.

When i revisit it I'm going to do the proper X degrees at Y kpps for the ilda test. I think the slower ones will be ok at 12k, but i'd like to run them as quickly as possible to make the most of the other ones. If they go pop (do scanners go pop, or more a graunch/grind or just a fizz?) then its a good excuse to replace them with something a bit better, they were cheap in the first place!

Another Adam

[Frixxion]

Hi all,

I have built the Norm Galvo kit and at the moment it is working fine. I have done some tuning and have found out that it is hard . But I have one small problem that I haven't read yet in this thread. Norm's galvo kit has 5 potmeters that you can play with:
- Low frequency Damping
- High frequency Damping
- Gain
- Command Size
- Torque
But I have absolutely no idea what to do with the Torque :S. Do you guys have any idea on how to set this potmeter?

[Mr.Coffee]

I would venture to say that "torque" would equate roughly with acceleration, and could possibly be used to adjust overshoot/undershoot with your damping. as far as "command size", that sounds very much like gain, but since you have a gain, I would check your schematic to see what it does to the signal path (Also known as "gain structure" in the audio world), I think that these are used to set a base setting, and may be able to be tweaked.
honestly, i'd wait to see if BB weighs in on this, as he is the scanner guru progenitor, and probably knows what those pots are.

[allthatwhichis]

But I have absolutely no idea what to do with the Torque :S. Do you guys have any idea on how to set this potmeter?

I know exactly what to do with it... NOTHING. King Pango stated you only use the HFD, LFD, and Gain when tuning. Leave the other two alone. If anything, ask Norm...

[carmangary]

^ Yea but if he built the kit from scratch he has to set it somewhere. He can't just leave it where it happened to be set when it came out of his parts bag.