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Thread: Auto dimming LCD

  1. #11
    Maximum Bitrate gork's Avatar
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    iPal:

    I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

    The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

    Illum wire at 0V -> Backlight powered at 12V
    Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
    Illum wire at 12V -> Backlight powered at 12V

    Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

    Again thanks for the help.. I wish my car had an easy solution like yours..
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  2. #12
    FLAC Mastero's Avatar
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    Aug 2001
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    India
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    nice my kind a place !

    I am also looking for the same solution to control the backlit with a dimmer.

    What i was thinking was to have a seperate 10k pot resistor to control the backlit seperatly. not through the factory dimmer.. dont know what my car works on its a MB shall know in a couple of days ..

    Mastero

  3. #13
    Constant Bitrate
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    Sep 2003
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    LA, CA
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    so u can not find any regular light bulb which controlled by dimmer in your whole interior?
    i don't quite understand how your interior lights work...
    what u mean by illum wire and backlight powered?
    hope u finding way to do yours...
    here is my video of my new interior...

    http://www.imagestation.com/video/vi...210992480&dl=1

    u have to click right then save it as different name to download... then play it~


    Quote Originally Posted by gork
    iPal:

    I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

    The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

    Illum wire at 0V -> Backlight powered at 12V
    Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
    Illum wire at 12V -> Backlight powered at 12V

    Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

    Again thanks for the help.. I wish my car had an easy solution like yours..

  4. #14
    Newbie
    Join Date
    Mar 2003
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    43
    wut about using a phototransister?

  5. #15
    Low Bitrate
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    Dec 2003
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    65
    Quote Originally Posted by gork
    iPal:

    I ripped open my dash again tonight to take another look at this... I took apart the dash module where the dimmer is located. No luck. It's all electronic. On further inspection, this makes a lot of sense as the interior illumination is a mix of LED, EL backlighting, and Incandescent bulbs. It seems the illumination brightness is varied from 1-12V via PWM on the illumination wire, though I cannot 100% confirm that it is PWM since my multimeter reads true RMS and my oscilloscope is currently out of commission.

    The problem I have with powering the inverter off of the Illumination wire is mainly that when the headlights are off, the wire is at 0V .. that would mean no backlight! also, at 1V the inverter would probably not even be able to power the CCFL.. I think what I really need is a circuit that somehow does this:

    Illum wire at 0V -> Backlight powered at 12V
    Illum wire at 1V (minimum dash brightness) -> Backlight powered at 5-6V or whatever the minimum voltage the CCFL lights at..
    Illum wire at 12V -> Backlight powered at 12V

    Unfortunately, I know only enough to be dangerous with circuits. I know there has got to be some simple solution to this problem, but I have no idea what it is :-/ This could help a lot of people too to have a workable way to dim the LCD backlight with the rest of the dash...

    Again thanks for the help.. I wish my car had an easy solution like yours..
    I am looking for a circuit to do this:
    Illum wire at 0V -> Backlight powered at 5V
    Illum wire at 12V -> Backlight powered at 3V (may be different)

    Does anyone know how I can go about doing this?

  6. #16
    kuo
    kuo is offline
    Variable Bitrate kuo's Avatar
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    hey ipal,

    what kind of screen are you using? i have a xenarc. will your method work with my screen? i'm very interested in doing the same thing. auto dimming the backlight would be very very cool.

    thanks,
    kuo

    Quote Originally Posted by Entcee
    I am looking for a circuit to do this:
    Illum wire at 0V -> Backlight powered at 5V
    Illum wire at 12V -> Backlight powered at 3V (may be different)

    Does anyone know how I can go about doing this?

  7. #17
    Low Bitrate
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    Dec 2003
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    Quote Originally Posted by kuo
    hey ipal,

    what kind of screen are you using? i have a xenarc. will your method work with my screen? i'm very interested in doing the same thing. auto dimming the backlight would be very very cool.

    thanks,
    kuo
    Most likely it would work. I just have a 2 line by 40 character LCD from www.CrystalFontz.com. Not 100% sure yours will work the same, but I would think so.

  8. #18
    Constant Bitrate
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    Sep 2003
    Location
    LA, CA
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    140
    just find power wires on inverter and connect one of them to dimmer controller on your car...
    you need to figure out if dimmer system is negative or positive...




    Quote Originally Posted by kuo
    hey ipal,

    what kind of screen are you using? i have a xenarc. will your method work with my screen? i'm very interested in doing the same thing. auto dimming the backlight would be very very cool.

    thanks,
    kuo

  9. #19
    kuo
    kuo is offline
    Variable Bitrate kuo's Avatar
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    i've got my xenarc dimming with the interior lights. my only problem is that when the lcd is dimmed there seems to be a lot of interference. dark horizontal lines travel from the top of the screen to the bottom. when the lcd is at full brightness these lines don't appear. any suggestions would be greatly appreciated.

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