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Thread: VARIABLE output modulation circuit?

  1. #1
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    Default VARIABLE output modulation circuit?

    Could anyone recommend a good, stable VARIABLE output modulation circuit to use with analog laser modules?

    I would like to be able to "manually" adjust beam intensity during setup, testing, "experimenting", etc. without requiring a connection to a DAC and computer.

    Thanks!


    RR
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  2. #2
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    A simple adjustable power supply will do the job... This is how I do that

  3. #3
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    Or just get a 5v P/S and a potentiometer to hook to the analog input.

  4. #4
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    As far as I know, this should work:
    .................______
    + 5V -------| 10k | ------------------------ ground
    .................-------
    ......................^
    ......................|
    ......................-----(+) laser input (-)----- ground


    ignore the ..., it seems that good old ascii art does not work on this forum..
    Last edited by Zoof; 07-11-2007 at 07:04.

  5. #5
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    .................................................. ..............................
    Attached Thumbnails Attached Thumbnails analog.JPG  


  6. #6
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    Cool - much simpler than I thought!

    Thanks!

    RR
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  7. #7
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    Hi Stuka,

    Yes the circuit suggested by Zoof and Steve is all you need.

    But make sure that your 5V source is a regulated power supply, or use a voltage regulator. There are many 5V supplies which say "5V" on the label, but these are unregulated supplies (i.e. the voltage with no load is more than 10 or 15 volts and will destroy your analog input circuit or overdrive the diode!

    Kind regards,

    sonaluma

  8. #8
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    Further note: DON'T LEAVE IT CONNECTED IF THE LASER IS SWITCHED OFF!

    Some lasers are fine, others can be fried by a 5V input on the mod input if no other power is applied. It's NOT a good thing to gamble on. The easiest answer is probably to use a pot as low as 1K, then feed from the pot slider through a fixed 10K resistor to the mod input. If that causes the control to sag a bit, it tells you two things: 1, you're safe. 2, you're only safe because you did this.

    A laser with a proper protection will be buffered with a high resistance input so the voltage you feed it won't do anything unless the buffer is supplied with internal power.
    Last edited by The_Doctor; 07-12-2007 at 05:57.

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