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Thread: My Quad 445

  1. #11
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    whats the size of that beam please.... nice efing build....
    Lasers, Lights, Music, Action!

  2. #12
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    A question about the positioning of the driver. Is it your plan to include some telescope/lens mounts to allow the user to customize beam size, or prisms to adjust aspect ratio? If so, that space adjacent to the driver looks good. If not, then reversing the position of the array and the driver would help to keep the wires in check. Just a thought.

  3. #13
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    gashead is offline Admin Verified: Best Accent Ever(Tm)
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    Bugger,

    I forgot to take a look at the weekend Andy! and hit you up on info about something in the red flavour!

    Still, what a wicked weekend!

  4. #14
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    lol theres always another meet.

    this module was posted today so no longer mine
    Eat Sleep Lase Repeat

  5. #15
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    Quote Originally Posted by dave View Post
    Series, you wont kill all the diodes if one decides to go open circuit..
    Hi Dave, a bit off topic but thanks for the invoice (WPs and die4chills)!

    Back to topic.

    I have Andy's prototype quad RED and after boxing it etc. two of the diodes suddenly started to just glow dimly. I assumed a die4drive component had given up its smoke since they were both driven by the same board, but Andy suggested checking the diodes first.
    On reflection, and given that advice, I have realised that if they are in parallel and set up for the d4driver to supply a given amount of current, and also since they have no series resistors (to avoid unnecessary heat one would suppose), then if one diode goes the other could receive much more current and also blow immediately.

    This would depend a lot on HOW the Laserdiodes tend to blow.

    Then I saw your comment here!

    Questions:
    Do they always or at least usually blow tending to higher resistance/voltage drop or even open circuit ?

    If they go "open circuit" how do they manage to "glow".

    Is there any way of protecting the "other" diode/s in a parallel wiring setup, which does NOT generate more heat when running normally?

    If not the series/parallel decision is not so much of a "personal preference thing" rather a very wise and necessary precaution to decide to always have them in series.

    How many leds (in series) would one have to use in parallel with each LD so that they would not affect normal working setup but would indicate which LD was blown if two or more LDs and LED sets were wired in series?

    Cheers
    Last edited by catalanjo; 04-08-2011 at 16:12. Reason: Tea break

  6. #16
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    In my experience with killing a couple of dozen diodes I have yet to see one truly "blow". Rather, when wired properly and not in reversed polarity the common failure site is optical and as such the cavity is no longer able to support laser action, but the junction still exists as in any LED and so it still outputs light, but poorly and the electrical characteristics remain relativley the same. Of course the lack of laser output does effect the resistance of the diode,but this is minimal. I can't recall what the electrical properties were like after I accidentally reversed the polarity. I do not understand what the advantages of parrallel operation are other than accommodating the use of a lower voltage driver. Cassio operates their projector modules with 4 series of 6 445 diodes. So, I guess it can be done both ways.

  7. #17
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    @planters

    " the common failure site is optical and as such the cavity is no longer able to support laser action, but the junction still exists as in any LED and so it still outputs light, but poorly and the electrical characteristics remain relativley the same."

    Why would two LDs go spontaneously together then?
    The only thing they have in common is the driver!
    One of the LDs is "extremely near its knefe edge mirror so optical feedback noise is possible but the other is much further away and so optical feedback is doubtful.

    I also do not understand Dave's comment if what you say is in fact the case. Am i missing something obvious here ?

    Cheers
    Last edited by catalanjo; 04-11-2011 at 04:00. Reason: fat fingers

  8. #18
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    Despite what I said, I only run multiple diodes in series because I agree with Dave that it is safer and you have no need to worry about current balance. You always have to wonder what the cause of the "first" failed diode was as it might be a voltage spike or ESD that fried the second diode at the same time.

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