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ArcticMyst Security by Avery

Hello everyone! Scanner questions

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Mar 18, 2013
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SO. i have a handful of little galvos, by symbol technologies (oh no, not one of those guys!) and i was hoping to get a little help understanding them. there's a few things i know about them, after diggin around the internet, but i need just a little more help understanding what i got going on here.

bias current to the black/red wire pair, and a variable voltage to the other pair.

Red / Black wires - Bias Current
Yellow / Blue wires - variable current

It is rated for 12 to 14 volts, according to the internet, evidently. i'd like something that resembles confirmation but will settle for whatever i can get :)

In most all of the things i'm reading, i am having trouble finding relevant information about exactly how to wire these up. i ASSUME i'm going to ground the black wire, apply 12 volts to the red wire, and ??? with the variable current wires. Do i attache say blue to ground and then pass -12 to +12 volts to the yellow?

I would appreciate any help you guys have to offer in this. thank you for your time.
 





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859511_4330301786555_1562795719_o.jpg


fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-prn1/859511_4330301786555_1562795719_o.jpg

i'll have to get home from work to take better photos... :p

the schematics look promising, and i'm currently browsing them now :)
 
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Mar 18, 2013
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my biggest problem is knowing how many volts to supply the 'bias' w/. or if that bias is always set to that value or if it is variable at all.
 
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I cannot recall ever trying to explain this to someone, so I’m going to give it a shot more to teach myself than to teach you. Those tidbits I get wrong, maybe someone can chime in and help me get it right. Some of this is discuss on Wikipedia - Laser projector

The very basic signal to drive a scanner is a sine wave. If you place two scanners at right angles, and you feed one of them a sine wave, and the other a cosine wave (a sine wave 90-degrees offset from the first sine wave) then, all things being equal, it should draw a nice pretty circle on the wall.

The signal typically goes through an amplifier, tuned specifically for the needs of the scanner. Typically, the maximum amplitude of the input signal is 10 Volts, peek to peek. (Or is that +/- 10 Volts, meaning 20 Volts peak to peak?) Anyway, the amplifier goes between the input signal and the output device (in this case, the galvanometer or scanner.) Very much like your home stereo system.

Two basic types of scanners exist, “open loop” and “closed loop.” Closed loop scanners have feedback coming from the scanner, and as such, have a greater number of wires (three more, typically). Your scanners look more like DC motors than the common scanner we recognize, today. But that is not to say you cannot get them to work.

modern-galvo_zps9a3c7573.jpg


You can forgo the galvo “driver board” if your input signals have the correct voltage and sufficient current. But one way or the other, you will need to correctly amplify your signal. This may, of course, be done more easily with a separate driver board. The specs, if you can find them, of your galvos will tell us (and you) much of what they need and want.

Attached is an image of a close-loop driver schematic I found on the net, somewhere. It may be of use to you. I save it, because it's sufficiently tunable, and it may suit your needs once you know the limits of your scanners.

Whoops, the schematic is too large. But it may be viewed from: http://i1290.photobucket.com/albums/b530/pschlosser00/LPF%20attachments/closed-galvo-amp-schematic_zpsd19fd1a2.png
 
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*nods* the problem is with symbol technologies stuff is they refuse to service it or help diy guys like myself.

I will see what i can't do about borrowing a function generator w/ two channels and attempting to drive the galvos, i'm just really concerned i'm going to nuke the poor thing. lol. i run on a shoe string budget, which is to say i don' thave the money for shoe strings, so all of my stuff is 'junque' saved from other things :p

makes it cost a lot less, but i do get stuck w/ the 'how the hell does this work' problem. That problem is right now Symbol was bought by Motorola, integrated with their hand held UPC scanner systems, replaced with a mirror array and is no longer galvos, and now they don't even want to talk to me, much less let me have a datasheet for their motor. Frankly, i'm tempted to tear apart the third galvo so i know how the other two work. :p
 
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I think those may be stepper motors, not galvos. The mirrors you have in the picture look quite heavy as well, which wouldn't work well on a galvo.

Try performing a continuity check between pairs of wires to see if they're connected. You'll need a driver of some sort regardless.
 
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hmm. i looked very closely at them, no brown wires. maybe the part numbers are close but not the same?
 
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Mar 18, 2013
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ok. I've looked even closer at them:

734092_10151554880895449_1796820909_n.jpg


544422_10151554880905449_939031657_n.jpg


599647_10151554881255449_1312230559_n.jpg


i've never seen a stepper motor in that arrangement. I'm not entirely sure what i'm looking at now, or how to utilize it. don't worry, i have 2 more left :p
 
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It looks like it's a 2-phase brushless motor, maybe stepper. The red and blue control one pole, the black and yellow the other.

If you want to work with real galvos, you'd probably be better of buying a real galvo kit.
 
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the truth of the matter is its what i got to work with :p what its looking like is i charge one coil, and variable the other to get movement, but i dont know that for a fact, and i'm hoping one of you guys or gals might have the magic bit of info to help me make this more than a dream.

I don't need to even achieve the ilda. i'm good with beam affects. and if i can get 7 or 9 beams at a time through POV, i'm perfectly happy :p
 
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Well, you could try hooking each coil up to a half-bridge chip or some transistors and see about controlling it that way. I tried that with a regular three phase motor and one of these, but ended up burning out the chip. You might be able to get something like that working.
 




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