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Thread: backlight flickers on 40x4 LCD, HELP!

  1. #1
    Variable Bitrate
    Join Date
    Apr 2000
    Location
    Little Rock, Arkansas
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    321

    Angry backlight flickers on 40x4 LCD, HELP!

    Just recently put my 40x4 LCD into my car and as Im riding down the street my backlight will begin flickering. Not sure why or anything. Doesnt flicker with the sound of the bass or what not. One note is that I did not connect a pentiometer to my backlight signal as it is shown in several schematics. Surely this isnt the cause. Any case, need a few suggestions.

    Thanks,

    Grand Am-P3
    The Grand aMP3 Project
    Car: 96 Pontiac Grand Am
    Current Setup: AMD K62 300MHz, 64MB DIMM RAM, 20GB WD Hard Drive, Basic Video & Sound

  2. #2
    FLAC
    Join Date
    Aug 1999
    Location
    Upper Marlboro, MD 20772
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    1,311

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    Mine use to do that. It turns out that the +5v is not clean or strong enough. Even my TFT screen FEW days ago did the same thing. For the time being, i connected it to the cigarete lighter and it stoped. If u are geeting ur +5v from the PSU and ur psu i not connected directly to the battery, then my suspecion is that the alternator is disturbing or afftecting the current, i believe ppl refere to this as that sine wave thing. Either way, ur current is not clean. Also check the wire that supplies the +5v to the LCD.

    abcd-1.
    abcd-1
    Author of CobraI,II,III and now CobraIV.
    You can contact me on AOL instant messenger....nick is cenwesi or cenwesi3

  3. #3
    Newbie
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    Jul 2000
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    Syracuse, NY, USA
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    I had a similar problem. Re-soldered all the connections and made sure everything was good and solid. That seemed to clear things up. The trick is definately a clean current (my PSU/inverter is wired to the Battery which seems to be clean enough). Also make sure you remove any kind of ground loops, that can have just as bad of an effect.

  4. #4
    Variable Bitrate
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    Apr 2000
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    Ive got my inverter plugged into the fuse box in my car. Ive got the LCD plugged into the 5V from the PSU on the computer. The wire Im using isnt very heavy of a guage at all, might it be the cause? Another note is that the power supply is probably 5-7+ years old. My alternator is just newly rebuilt, so surely thats not it. Anyway, thanx for the suggestions so far.

    Grand Am-P3
    The Grand aMP3 Project
    Car: 96 Pontiac Grand Am
    Current Setup: AMD K62 300MHz, 64MB DIMM RAM, 20GB WD Hard Drive, Basic Video & Sound

  5. #5
    Newbie
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    Jul 2000
    Location
    Syracuse, NY, USA
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    Well, the age of the power suply shouldn't matter that much (as long as it's working at all). Mine's pretty old too.

    How far is the LCD from your CPU/PS? Are you running wire all the way from the trunk to the dash? That's the way mine is set up, so instead of running the +5v through the parallel cable, I ran a separate set of lower guage wires (not much lower, but mainly to put some distance between the sheilded data cable and the power). It's the same thinking as running the power and audio down different sides of the vehicle to reduce the risk of interference.

    Still, is it just the backlight that is flickering or the characters too? Do you hear any alternator whine in the audio? If so, check the ground loop situation first.

  6. #6
    Variable Bitrate
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    Apr 2000
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    Little Rock, Arkansas
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    Its the characters and the backlight. But I think Ive solved the problem. Ive turned my contrast down the tiniest bit and so far it doesnt seem to have flickered. The real test though will be tonight after dark. But in daytime, the characters arent flickering now. Im running the parallel and the power seperately, just simply didnt feel like hacking into the parallel cable then hacking out of it. Im not using a ground loop isolator in my setup, instead grounded the psu to the car body. But as of right now, seems situation is under control, will post again with the results after tonight. Thanks for both your help. Tremas, uve been added to my imaginary list of valued mp3car.com users (cenwesi u were already on there).

    Thanks again,

    Grand Am-P3
    The Grand aMP3 Project
    Car: 96 Pontiac Grand Am
    Current Setup: AMD K62 300MHz, 64MB DIMM RAM, 20GB WD Hard Drive, Basic Video & Sound

  7. #7
    Newbie
    Join Date
    Nov 2000
    Posts
    18

    Post

    are you sure you have a +5 DC backlite??

    if its an LED backlite then it probably is

    but if it is an EL backlite, then it takes an AC current (usually a small 80v 60hz inverter is included.. about 1"x.5"x.3" .

    That would also account for your flickering.


    ~Paul

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