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Thread: Modulation?

  1. #1
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    Default Modulation?

    Probably a very dumb question, but-

    If i use different laser modules with different analog modulation rates is that going to cause any foreseeable problems? 473nm say at 10khz, 635 at say 15khz, and 532 at say 20khz? or any combinations thereof.
    thanks.
    -Marc

  2. #2
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    Default

    I would say that it would probably be fine, you may run into issues as you approach the max blanking speed of each of the lasers. also, if they have different rise time, that could produce a possibly noticeable difference.

    on a similar note, My first projector is going to be a dpss blue (i'll upgrade it to RGB later, I plan to cut the learning curve up into chunks). my question is, for one laser, would analog or ttl be better? I can't see where graphics would need dimming, but would the analog look cleaner? btw. this is a 20khz analog. would the ttl be faster? if so would it be better to use ttl?

    my inkling is to stick with analog, as I do plan to go rgb in the future, and I figure that would make for fewer programming changes down the line.
    "TO DO IS TO BE" - Nietzsche
    "TO BE IS TO DO" - Kant
    "DO BE DO BE DO" - Sinatra

  3. #3
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    Default

    mr coffee- (as im drinking a big, nice, hot cup of coffee! lol..)

    anyway-

    GO ANALOG!!! especially if you are building this in chunks to make it more affordable. for the price difference now of only $50-$100 MAX for an analog modulated laser, it will save you THOUSANDS later! (Actually, most laser manuf. dont really charge more for analog anymore. especially the chinese lasers) and it will save you COUNTLESS upon COUNTLESS hours of rebuilding and/or headaches later on, down the road going form TTL to analog!

    TTL is too limited as to the color mixing capabilities. the laser is eitrher ON or its OFF. no in between. just make sure the software you get or design has analog signal output.

    -Marc

  4. #4
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    Default

    sorry for the couble post-

    but also,
    i like the "dimming" capabilities on lasers. to me, if youre a good operator, the dimming can be used as an effect in itself. adds dramatic effects to diff parts of shows i think.
    laser turns on reaaal dim....

    song builds up....

    laser gets brighter....

    song plateus....

    laser starts sweeping....

    song goes crazy!!!!!

    LASER GOES CRAZY!!!!!

    woooweee......

    just my opinion of course!

    -Marc

  5. #5
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    Cool

    Getting back to the blanking speed question for a second...

    If you have different blanking speeds you will notice goofy color tails on your graphics. This is caused by your fastest laser coming on before the others.

    It's not always noticeable, but it is a bit of a bother. The only way to get rid of it is to build a delay circuit into the blanking lead of the fast laser and slow the signal down to match the response of the slower lasers.

    I currently have this exact problem with my projector, because my Maxyz modules are *screaming* fast, while my green is only rated at 10Khz. So when I'm displaying a yellow line, it has a red tail at the beginning.

    In fact, even though my blue laser is rated for 20 Khz, it's still not fast enough to keep up with my Maxyz modules. So a purple line will also have a red leading tail on it.

    I'm going to build the delay circuit that Bill Benner suggested. I just haven't had time to do it yet.

    Adam

  6. #6
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    Default

    You could use one of my magical filters to straighten this out. You can read about it here:
    http://www.pangolin.com/resguide03d.htm

    Note that there is a really complicated circuit shown, but all you really need is a dual-slope low-pass filter, such as the one shown here:


    Best regards,

    William Benner

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