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Thread: Question about driving un-isloated diodes

  1. #1
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    Default Question about driving un-isloated diodes

    I am working on building a multi-diode setup using much of Andycon's work as a template.

    The main goal of this build is to save money where-ever possible (besides cheap mounts) so I want to use a Flexmod P3 to power 6 LPC-815 diodes (LOC red diode).

    My setup would have two sets of 6 diodes with each set one powered by one flexmod P3. The diodes are not isolated from each other and would be run in parallel. Running diodes un-isolated in parallel has worked for me before but I did not use two different drivers so I don't know how it would work.

    Is there going to be okay with the diodes un-isloated?
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  2. #2
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    Default

    I am doing very similar to you, running 4 x LOC from a single Flexmod P3.

    I wired a 1ohm 1/2W resistor in series with each LD (on the +ve connection) to balance out small variances with the LD forward voltage so that they all run very similar current.

    Another benefit of doing this is you can measure the current to each diode by measuring the voltage drop across each resistor, mV = mW.

    If you can, use 1% metal film 1/2W resistors. For one they won't fatigue like carbon resistors do, and second they are 1/2W in the same size package as a 1/4W carbon resistor.

    At 420mA, the volt drop is 420mV. The power dissipated by each resistor is therefore 0.42V x 0.42A = 0.1764W.

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  3. #3
    Join Date
    Sep 2010
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    Utrecht The Netherlands
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    Default triple red in block, not isolated

    Question, i have a nice block to put my three red diodes in.
    If they are not electronic separated, the block and colimator casing is connected, should i run them parallel or in serie (i would think parallel and with the 1 ohm resistor on the laserbug)? I can also put some kapton tape around them to isolate the collimators from the block.
    I have one flexmod to drive my three red LPC815 diodes and want to use knife edging to create the beam.

    Michel

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  4. #4
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    Michael, like in my build with LPC-815 LOC's (case negative) you have two choices:

    1. Isolate the mounts and wire them in series;
    2. Non-isolated in parallel with 1ohm series resistors on each LOC AND a high side driver.

    Cheers.
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  5. #5
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    Default

    Quote Originally Posted by MisterWilling View Post
    I am working on building a multi-diode setup using much of Andycon's work as a template.

    The main goal of this build is to save money where-ever possible (besides cheap mounts) so I want to use a Flexmod P3 to power 6 LPC-815 diodes (LOC red diode).

    My setup would have two sets of 6 diodes with each set one powered by one flexmod P3. The diodes are not isolated from each other and would be run in parallel. Running diodes un-isolated in parallel has worked for me before but I did not use two different drivers so I don't know how it would work.

    Is there going to be okay with the diodes un-isloated?
    Click image for larger version. 

Name:	photo.JPG 
Views:	78 
Size:	398.0 KB 
ID:	22178
    one question would be, is using 12 diodes how are you alignment/stacking them? what sort of beam are you trying to get out?
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  6. #6
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    Quote Originally Posted by andy_con View Post
    one question would be, is using 12 diodes how are you alignment/stacking them? what sort of beam are you trying to get out?

    in case it is of any interest, i am thinking something like

    xxxx
    xxxx
    xxxx

    assuming a 3x5 dot from each loc and cliping the 5mm slightly, i want to be close to a beam od 12x13 mm. then run it through 3:1 telescopics
    "its called character briggs..."

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