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Thread: Galvo Driver Input Wiring Questions....

  1. #1
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    Default Galvo Driver Input Wiring Questions....

    Hey Everyone,
    I'm getting ready to hardwire everything together on my beam table. I have a program board that came with my galvo parts as well as a DAC board. Can I just splice the DAC board into the wiring of the program board? I'd imagine if I use a three position switch to control either one or the other board being on, I shouldn't have a problem right? I just don't want to run into an issue where the backfead signal to the un-powered board will mess with the signals going to the drivers. Oh, same thing for the laser TTL....
    Thanks!
    Adam

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    Cool

    I'm not sure exactly what your question is...

    The program board you speak of - is this an analog waveform generator? (A lissajous generator?) So you're thinking about connecting it directly to the galvos, and then installing a switch so you can select whether the output from the DAC or the output from the analog board is sent to the galvos, right?

    In that case, are you thinking about using the 3 position switch to control power to either the DAC or the analog board and wiring all the outputs together and runing them to the galvo inputs? Or are you actually wanting to do the switching at the input to the galvo amps? (Which would require a minimum of 2 contacts, assuming you used single ended connections and a comon ground between the DAC, the analog board, and the galvo amps.)

    If it were me, I'd go with the latter approach. I'd do the switching at the input to the galvo amps using a DPDT switch with a center off position. Conenct the X and Y grounds on the amps together and tie them to the X and Y grounds for both the DAC and the analog board. Then connect the DAC X+ & Y+ to one side of the DPTP switch, and the analog board X+ & Y+ to the other side of the switch, and then connect the center taps on the switch to the X+ and Y+ input on your scanner amps.

    As far as the TTL blanking on the lasers - again I'm not sure what you're asking here. Does your analog board also have a TTL blanking output? If so, then I'd wire it the same as for the X & Y above. (Tie all grounds together and use the positive blanking wire as your switched leg.) If you're talking a monochrome projector you only need a SPST switch. But if you've got an RGB rig, then you're going to need a QPDT switch or a quad-pole relay. (Technically you'd only have three lines to switch, but three-pole switches are uncommon items...) And this assumes that your analog board has three separate TTL outputs. (Never seen one like that...)

    Adam

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    Default

    Hi Adam,
    Yes, you got it. I'm actually starting off with an RGY setup and yes, both the program board and the DAC have separate TTL outputs for each color. While I understand what your getting at, It would obviously be easier switching from the power to either device, that's optimally what I'd like to do if possible. I would probably need to wire up a relay board to switch all those connections as you suggest, which I may have to if you think I'm going to get interference.
    Thanks!
    Adam

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    Smile

    It's not so much the interference I'm worried about, as the fact that upon inital power up (and power down, for that matter), the outputs of both the DAC and the analog board can get a little... wonky. You wouldn't want the galvos to shoot off in a goofy direction like that if you decided to switch positions in the middle of a show.

    A relay board would probably be the best thing to do, since you need to switch the X & Y signals plus the TTL color signals all at the same time.

    Off topic here, but is there any chance of you attending SELEM this summer? I know it's a hell of along way from Milwaukee, but I think you'd enjoy seeing some of the different projector designs that will be set up there. And I'd like to see this setup you're building, too. Give it some thought anyway. (You might be able to get a cheap flight into Charlotte, NC. The auditorium is just under an hour's drive from the airport.)

    Adam

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    Quote Originally Posted by Buffo View Post
    It's not so much the interference I'm worried about, as the fact that upon inital power up (and power down, for that matter), the outputs of both the DAC and the analog board can get a little... wonky. You wouldn't want the galvos to shoot off in a goofy direction like that if you decided to switch positions in the middle of a show.

    A relay board would probably be the best thing to do, since you need to switch the X & Y signals plus the TTL color signals all at the same time.
    Okay, Well I never planed on switching the galvo driver input in the middle of a show. So, in theory, If I stoped the output from the DAC or program board befor I switch it over it "Should" be safe,,,, right? Ofcourse I'd test this in a controlled environment first to make sure the beam isn't going to fly far left, right or down. My biggest concern is that I'd try to connect it this way and blow a board or tweak the galvos by sending a bad signal. I guess worst case I'd dump the program board because I plan on getting a better DAC and software soon and won't need the simple little program board anymore.


    Quote Originally Posted by Buffo View Post
    Off topic here, but is there any chance of you attending SELEM this summer? I know it's a hell of along way from Milwaukee, but I think you'd enjoy seeing some of the different projector designs that will be set up there. And I'd like to see this setup you're building, too. Give it some thought anyway. (You might be able to get a cheap flight into Charlotte, NC. The auditorium is just under an hour's drive from the airport.)

    Adam
    Sounds interesting..... It just so happens I have some miles saved up and may be interested in hanging around with fellow enthusiasts. I tried looking up this event for info but couldn't find anything. Is there a website where I can get some info on this event? I'll see if I can post pics tonight of my project.
    Thanks!
    Adam

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    Smile

    Hi Adam;

    Re: SELEM... There isn't any other website. We've been talking about it right here on PhotonLexicon. Here are the relevent threads:

    http://www.photonlexicon.com/forums/...ead.php?t=2583
    http://www.photonlexicon.com/forums/...ead.php?t=2543
    http://www.photonlexicon.com/forums/...ead.php?t=2536
    http://www.photonlexicon.com/forums/...ead.php?t=2427
    http://www.photonlexicon.com/forums/...ead.php?t=2575

    Right now it's on for Satuday, August 18th and Sunday, August 19th at the Newton-Connover Civic and Performing Arts Center auditorium, located in Newton, NC. (We've had to change the location a couple times because of the extreme difficulty in finding a place that was both affordable and also would permit us to use fog machines...)

    This is purely a non-profit gig. We're asking the people that attend to share in the cost of renting the auditorium for the weekend. (Should be around $700 total, or around $70-80 per person, depending on the final number of people that can attend.) Beyond that, whatever equipment you want to bring is up to you. (You don't need to bring anything if you don't want to. Feel free to just come to meet the rest of us geeks and watch laser shows!)

    Re: your projector concept. I think if you powered the galvos off before you switched the power you'd be fine. I don't think you'll have any problems with feedback from one board causing damage to the other. On the other hand, if you want to use relays and switch it at the input to the amps, you won't have any problems either. Your call as to which way you want to go.

    I'll have a look at the pics later. (Firewall at work is blocking them).

    Adam

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