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Thread: What is with 445nM ghosting / beam suppresion ?

  1. #1
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    Default What is with 445nM ghosting / beam suppresion ?

    Hello all,

    Need some help/education; failed to get the blue to turn completely off now on TWO different lasers, there must be something I need to learn

    Well, I've failed on both lasers to get the beam to completely turn off at 0VDC analog or TTL input. The first laser was a TTL 1,000 mW 445nM TTL laser module from O-like with a sealed driver module. So I figured maybe the driver circuit was not set up completely correct and learned to live with it.

    But now since another projector is being built (isn't it funny how that happens?) I am having the same issue with (405 nM Osram Diode from DTR) and can't get the beam to completely shut off. And this time I'm using a Flexmod P3 driver. Changing the bias does not get get that dirty dog to turn all the way off. I set the diode's operating currrent (at 5VDC modulation input) to whatever the datasheet said (165mA I think).

    Is there something different about the blue Laser Diodes ? Perhaps I need a beam suppression option for the Flexmod ?

    Gentlemen, what am I missing ?

    Thanks!

    -Jason

  2. #2
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    I believe the beam suppression option would be a safe way to ensure you dump the dim LED, Jason. Unfortunately only DrLava/Innolasers sells this version of the P3, so you may be in for a wait after you order.

    I also recall someone saying that they used the balance adjustment on the P3 (the center potentiometer) to address this problem, I believe with a 520nm diode. That's not the point of balance adjustment as I understand it, but it might be worth a try (keeping track of any changes against the original location if you want to return to the factory settings). Personally, I've started using the beam suppression P3 with my latest builds and I've been quite happy with it.

    Good luck!

    -David
    "Help, help, I'm being repressed!"

  3. #3
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    use a spatial filter.

  4. #4
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    use a spatial filter
    Or one of Dave's drivers which feature beam suppression (as a very happy user of 4 of them, despite my best efforts to short circuit the bejesus out of them!)
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  5. #5
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    Default What do you do on a holiday weekend when it rains? + follow up on OP

    Quote Originally Posted by dkumpula View Post
    I believe the beam suppression option would be a safe way to ensure you dump the dim LED, Jason.
    What do you do on a holiday weekend when it rains? Work on your second PJ and learn how to set up some Flexmod P3s!

    Gentlemen, the Flexmod P3 with the beam suppresion option fixed the ghosting problem with the blue laser. Finally! fyi 'Interlock option not available' means do not wire the interlock - leave it float! I think I read this somewhere on this forum; otherwise you can't set up the flexmod's current correctly.

    Soooooo I moved the 'old' Flexmod from the blue diode to a new red (replacing the TTL board that came with the laser) AND guess what.... Now that one ghosts.... LOL So I think I learned all LDs can ghost. Maaaaaan gotta say I'm earning my analog, the TTL drivers from the manufacturers worked just fine. Retrofitting to analog is more of an adventure than I expected. A statement from Mixedgas sticks in my mind: "If you don't have analog, you are definitely missing something".

    Maybe I can retrofit my other P3 with a 47K and 1Meg resistor to suppress the red beam in standby? [If the P3 boards are the same?] Bias current adjustment did not seem to do it.

    On a lighter note, the RIYA DAC works great with LSX, my original PJ still has a bread boarded soundcard DAC and now I think an Etherdream DAC will replace that.

    *** So to those of you who build from scratch using P3's *** .... Do you think I can monkey with the bias/balance to suppress the 665nM red in standby?

    From two projectors three in the near future... What is happening here?
    Attached Thumbnails Attached Thumbnails Tivo chassis as a projector 2.jpg  

    Tivo chassis as a projector.jpg  


  6. #6
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    swamidog is offline Jr. Woodchuckington Janitor III, Esq.
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    you can't magically convert the non SBS version of a P3 to support SBS with a resistor change. SBS P3's have a different firmware.

    Quote Originally Posted by JasonB View Post
    Maybe I can retrofit my other P3 with a 47K and 1Meg resistor to suppress the red beam in standby? [If the P3 boards are the same?] Bias current adjustment did not seem to do it.
    Last edited by swamidog; 09-01-2014 at 19:07.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by swamidog View Post
    you can't magically convert the non SBS version of a P3 to support SBS with a resistor change. SBS P3's have a different firmware.
    Swamidog, thank you for this comment. I was hoping you were keeping an eye on me... You saved me some time and frustration here, and I really appreciate it!

    - Jason

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    swamidog's Avatar
    swamidog is offline Jr. Woodchuckington Janitor III, Esq.
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    as an ex-chicago dweller, it is my sworn duty!

    Quote Originally Posted by JasonB View Post
    Swamidog, thank you for this comment. I was hoping you were keeping an eye on me... You saved me some time and frustration here, and I really appreciate it!

    - Jason
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  9. #9
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    Quote Originally Posted by JasonB View Post
    From two projectors three in the near future... What is happening here?
    I think you know what's happening, Jason! Every time I add a new projector to my environment, I think of reasons why I want 1, 2 or 3 more . . . I suppose we should just be happy if you don't make it to Brad's level of coherent-light illness. . .

    Love the reuse of the TIVO box, by the way!

    -David
    "Help, help, I'm being repressed!"

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