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Thread: Weird ground-loop noise caused by touchscreen??

  1. #1
    Maximum Bitrate GingerPrince's Avatar
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    Weird ground-loop noise caused by touchscreen??

    Have installed touchscreen in my car this week. However it's now causing excessive noise in my audio system. Before it was fine, now I can hear the interference noises from the LCD.

    Really odd thing is that the computer doesn't even have to be on, just so long as my head unit is wired to my computers audio-out, and my touchscreen to the usb, and the LCD on, I get noise.

    I'm assuming it must be some sort of ground loop thing (the grounds will be shared through the computer somewhere between the USB port and the line-out port presumably) but I don't know how to sort it. There was no noise before with screen and computer plugged in so my grounds are good (all short runs, and straight to floor-pan).

    Any ideas how I can get round this? At the moment I've got a ground-loop isolator which is cutting a bit of it, but it still sounds craaaap!

  2. #2
    I'm sorry, and you are....? frodobaggins's Avatar
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    power your lcd from the pc power supply, then they will all be on the same ground
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  3. #3
    Maximum Bitrate GingerPrince's Avatar
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    Originally posted by frodobaggins
    power your lcd from the pc power supply, then they will all be on the same ground
    That doesn't work (at least until I get a better regulator for my supply). If I hand the LCD off the pc, then the cranking power for everything including the screen is too much and it won't boot. It I power the screen separately off the regulator, then it's already settled by the time I power the 'puter and it works fine.

    When I get a better supply I will power it from the computer, because for one thing the screens always on even if the computers off!

    I agree that should probably solve the noise issue though.

    Ta



    Sy

  4. #4
    Newbie matqua's Avatar
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    I had the same problem initially. It seemed to be a combination of the cheap 12V regulators for the screen and my cheap arse amp. Needless to say, i bought a good amp and the noise is gone.

    It is frustrating I know.

    Quote Originally Posted by GingerPrince
    That doesn't work (at least until I get a better regulator for my supply). If I hand the LCD off the pc, then the cranking power for everything including the screen is too much and it won't boot. It I power the screen separately off the regulator, then it's already settled by the time I power the 'puter and it works fine.

    When I get a better supply I will power it from the computer, because for one thing the screens always on even if the computers off!

    I agree that should probably solve the noise issue though.

    Ta



    Sy
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  5. #5
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    you can also add some large capacitors across the supply lines close to each device. this will help flattening out the power line.
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