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  • Whine from carpc

    After a few hours of searching and reading I still havent been able to fix this problem...

    My carPc is giving off that whine and slight buzzing noise. You hear it from the time the carpc starts up.

    Here's the thing now... As you accelerate the noise changes with it. I'm guessing alternator whine?

    Also, this only happens when im switching into AUX mode. I can play CD's and the radio without this happening.

    So I know for sure its the PC.


    I'm running two M2-ATX's


    My soundcard is ON-BOARD.

    I'm 100% sure the power supplies are grounded properly. I've sanded down the area clean and its getting good contact and its very secure.


    The RCA's are run on the right side of the car, there are no power cables there EXCEPT for the 12V line coming from the PC to power the Liliput

    (I havent tried moving the RCA yet but I cant think of where I could run it.)

    I've gone through the FAQ and the only thing I haven't tried is the ground loop isolater.

    Any suggestions on things to try?
    1999 Lexus GS300- (going VIP)
    1993 Lexus SC300-Turbo (Totaled by idiot driver)
    1996 Lexus SC400- (Totaled by brother)
    1972 Datsun 240Z- (WIP)
    1994 Toyota Camry- (sold)

  • #2
    try grounding from one of the mobo standoffs to the the M2's ground. since you are using onboard sound this will help greatly.

    Also you said you tried a ground loop isolator? Did you place it as close to the HU as possible or as close to the PC as possible?
    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

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    • #3
      Im going to try that 2k1 sounds like it could work.

      I haven't tried the isolater yet, That will be my next step.
      1999 Lexus GS300- (going VIP)
      1993 Lexus SC300-Turbo (Totaled by idiot driver)
      1996 Lexus SC400- (Totaled by brother)
      1972 Datsun 240Z- (WIP)
      1994 Toyota Camry- (sold)

      Comment


      • #4
        if you have to go the isolator route, then place it as close to the HU as possible.

        I thought you had already tried the isolator though?

        I've gone through the FAQ and the only thing I have tried is the ground loop isolater.
        Fusion Brain Version 6 Released!
        1.9in x 2.9in -- 47mm x 73mm
        30 Digital Outputs -- Directly drive a relay
        15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
        Buy now in the MP3Car.com Store

        Comment


        • #5
          Nope I didn't try. Oops i didnt see that mistake in my post =P
          1999 Lexus GS300- (going VIP)
          1993 Lexus SC300-Turbo (Totaled by idiot driver)
          1996 Lexus SC400- (Totaled by brother)
          1972 Datsun 240Z- (WIP)
          1994 Toyota Camry- (sold)

          Comment


          • #6
            These are absolutely classic symptoms of a ground loop.
            Old Systems retired due to new car
            New system at design/prototype stage on BeagleBoard.

            Comment


            • #7
              Just for clarification. Does a ground loop mean that one of the signal cables from the Car PC (like VGA, USB, Audio etc) makes contact with the ground from the car? I also have these irritating noises and i see lines walking over my screen. The lines also walk faster when the gas pedal is pressed (buzzing also gets a higher requency). I have a 12v+, switched 12v+ and a 12v- coming from the front off the car. Also my 12v+ from my Amp is running through there. I know its not the right way but i have to rearrange the power cables.
              If you`re not first, you`re last !

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              • #8
                No the ground loop is from varying electric fields mixes not so well with eachother. A wire running at 12v is putting out an electric field. Another cable lets say audio is using quite a few fequencies but not 12v. So the 12v electric field gets induced in the audio cable. So it is like adding this signal to the signal of the audio. If this wire was a constant 12v then there would be a buzzing but it would be a stable non pitch changing whine.

                Now that power cable is running off the car's alternator. THe alternator makes more current as the pedal is pushed down more meaning more rpms. So it is not a constant electric field. It gets bigger as your rpms get higher. So now add this varying electric signal to the audio signal and voila. You get this whine that goes up with the car's rpms.

                Now the same thing is happening with your monitor. It is visual noise instead of audio noise. Same thing with the singals getting scrambled. So you need to seperate the vga and audio cables from the power cable from eachother.

                The audio signals and vga signals do the same electric field thing. Any wire does. But the sources are so small that their fields are very small and usually don't penetrate the insulation of the wire and if they do it isn't that big of a radius.
                Fusion Brain Version 6 Released!
                1.9in x 2.9in -- 47mm x 73mm
                30 Digital Outputs -- Directly drive a relay
                15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
                Buy now in the MP3Car.com Store

                Comment


                • #9
                  Ground loops are to do with the two grounds for your equipment being at different potentials. Afaik it has little to do with magnetic fields and induction. You cannot solve a ground loop by moving signal wires away from power wires. You solve a ground loop by star earthing or a ground loop isolator to inductively couple the audio signal between the different grounds.
                  Old Systems retired due to new car
                  New system at design/prototype stage on BeagleBoard.

                  Comment


                  • #10
                    Originally posted by Rob Withey View Post
                    Ground loops are to do with the two grounds for your equipment being at different potentials. Afaik it has little to do with magnetic fields and induction. You cannot solve a ground loop by moving signal wires away from power wires. You solve a ground loop by star earthing or a ground loop isolator to inductively couple the audio signal between the different grounds.
                    not magnetic fields, electric fields. "electric potential" is voltage!

                    If it is just simple field on field action, then moving them away is easiest. This is of course assuming you have already followed rob's adivce and made good grounds.
                    Fusion Brain Version 6 Released!
                    1.9in x 2.9in -- 47mm x 73mm
                    30 Digital Outputs -- Directly drive a relay
                    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
                    Buy now in the MP3Car.com Store

                    Comment


                    • #11
                      Originally posted by 2k1Toaster View Post
                      not magnetic fields, electric fields. "electric potential" is voltage!

                      If it is just simple field on field action, then moving them away is easiest. This is of course assuming you have already followed rob's adivce and made good grounds.
                      Nope, sorry, your post still doesn't make any sense to me.
                      Old Systems retired due to new car
                      New system at design/prototype stage on BeagleBoard.

                      Comment


                      • #12
                        http://en.wikipedia.org/wiki/Electric_field

                        "Charges do not only produce electric fields. As they move, they generate magnetic fields, and if the magnetic field changes, it generates electric fields. This "secondary" electric field can be computed using Faraday's law of induction"

                        So the magnetic field changing induces a secondary electric field. Induction requires a magnetic field. Therefore I stand by my post.
                        Old Systems retired due to new car
                        New system at design/prototype stage on BeagleBoard.

                        Comment


                        • #13
                          I'm gonna try moving the RCA first to see if that helps with the noise at all or at least the buzzing. Then ill try shortening the grounds some more and grounding off a motherboard standoff. If not I'll give the ground loop isolater a shot.
                          1999 Lexus GS300- (going VIP)
                          1993 Lexus SC300-Turbo (Totaled by idiot driver)
                          1996 Lexus SC400- (Totaled by brother)
                          1972 Datsun 240Z- (WIP)
                          1994 Toyota Camry- (sold)

                          Comment


                          • #14
                            I`m going bald on my Car PC setup. For as far as i can see i tried everything. Few days ago i totally stripped my car and ran all new wires to my Car PC. I also separeted the power cables from the audio cables. I now know the problem is in my Car PC. I don`t really trust my M2-ATX. But the strange thing is that it works flawlessly on a seperate battery. So my Lilliput and all the rest of the crap is powered from the Car`s battery and the PC at that moment from a seperate one. Then all the problems are gone. I tried so many things already. I tried new cables directly from car battery (the inCar one), audio cables without the shield, started up the car pc and then pulled out all wires/cables except the 12v+, 12v+ switched, 12v- and audio cable and the the problem is still there. I have a FM Modulator (between antenna cable type) to get the sound on my stereo. I also have a Casette Tape to 3,5mm Audio Jack adapter and then the sound problem is less only the screen is still very noisy. Also i hacked ito the CD Changer cable and redirected the carpc`s audio through there and then the sound problem is also there, but when connected to the seperate Battery it`s gone. This happens when the car is not running and when the car is running i even have the alternator noise. I also tried a filter between the 12v+ of the pc.

                            Anyone else have some good advice? I already thought of buying a new M2-ATX to sort the problem out but i already spent a million on this damn thing.

                            Can you see my hair falling out
                            If you`re not first, you`re last !

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                            • #15
                              Plug your headphones into the PC...can you still hear the noise? It's the PC.

                              No? It is your wiring from the PC to the HU...or the HU itself.

                              Onboard soundcards are noisy anyway...mine has a high pitched whine that I can hear if the motor is off, the stereo is on, and the PC is on but not playing music.

                              If I run the PC audio at its max level, and turn down the HU, I never hear the whine when music is playing.

                              If I have the PC audio turned down...and crank the HU it is noisy as heck.
                              current projects

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