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Thread: 10 kOhm trimpots for controlling R,G,B intensity

  1. #1
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    Default 10 kOhm trimpots for controlling R,G,B intensity

    I added some trimpots to my old projector for controlling the intensity of the individual colors (really just needed it for overpowered blue but added to all modules anyway. I thought 10 KOhm was a good one to go with for a 5V ilda signal but at the lowest position of the trimpot the module still outputs some 50mW power (from 300). Am I using the wrong resistance trimpot?
    Or does this have to do with bad module driver bias or something?
    The trimpot is connected to the R, G or B + signal cable.

  2. #2
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    Depends on the trimpot.
    Some trimpots don't go completely to 0 Ohms and 10K ohms
    at the end points through the wiper.

    Jerry
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  3. #3
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    Oct 2016
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    Would make perfect sense, but the multimeter readings seem 100% correct, 0 kOhm to 10 KOhm. Unless I'm missing something with these tests.

  4. #4
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    Hello,

    sorry for saying that but it sounds like you didnt wire them as Voltage Divider and they are just in Series inside the Modulation Line.
    So the Wirering should be Mod -> Pot In and Pot out to GND, Lasermodul connected to the wiper.
    Greetings
    Guido

    www.mylaserpage.de

  5. #5
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    Quote Originally Posted by Guido View Post
    Hello,

    sorry for saying that but it sounds like you didnt wire them as Voltage Divider and they are just in Series inside the Modulation Line.
    So the Wirering should be Mod -> Pot In and Pot out to GND, Lasermodul connected to the wiper.
    Exactly, well pointed. And Linear type, not Logaritmic.
    Last edited by jors; 07-25-2017 at 06:56.
    Jordi Luque


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  6. #6
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    Oct 2016
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    I left one of the pins unused, so it has to go to ilda signal GND for this to work ?

    Quote Originally Posted by jors View Post
    And Lineal type, not Logaritmic.
    Are you saying a problem can arise when using linear trimpots instead of log pots, or the opposite? I thought in every case when you need to not adjust it once and leave it but need readjusting from time to time you get a log pot.

  7. #7
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    Quote Originally Posted by Finale View Post
    I left one of the pins unused, so it has to go to ilda signal GND for this to work ?


    Are you saying a problem can arise when using linear trimpots instead of log pots, or the opposite? I thought in every case when you need to not adjust it once and leave it but need readjusting from time to time you get a log pot.
    Hey take a look...one POT/ each colour.
    Click image for larger version. 

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  8. #8
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    Thanks.
    What the difference between log and linear here?

  9. #9
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    just googleing a bit 'n' copy-paste :

    "Linear POTs vs. Audio POts (logaritmic)

    Potentiometers, or "pots" to electronics enthusiasts, are differentiated by how quickly their resistance changes. In linear pots, the amount of resistance changes in a direct pattern. If you turn or slide it halfway, its resistance will be halfway between its minimum and maximum settings. That's ideal for controlling lights or a fan, but not for audio controls. Volume controls have to cater to the human ear, which isn't linear. Instead, logarithmic pots increase their resistance on a curve. At the halfway point volume will still be moderate, but it will increase sharply as you keep turning up the volume. This corresponds to how the human ear hears"

    so with linear POT, at 50% for example, you'll get about 2,5V modulation ie 1/2 Power..etc
    http://www.poeticmonkey.com/ebay/res...eter-types.gif
    http://doktorsewage.com/wp-content/u...entiometer.jpg
    Last edited by jors; 07-24-2017 at 07:33.

  10. #10
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    I think you are way off the mark. Just turn the current down on the blue driver to match the others. Otherwise you are losing dynamic range. You want the modulation to be full 0-5v. If you make it 0-2v you just cut you control range.

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