Noise problems

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  • Rob Northen
    Senior Member
    • Jan 2010
    • 137
    • Denmark

    #1

    Noise problems

    I've made a little project with an Arduino, interfaced to a VFD.
    It works great, except when I turn something on or off in my house, ex. a lamp. Then the txt on the VFD goes crazy, and I need to reset the board.

    A few things I've tried;
    -Running the board off diffrent power supply's (5v) both switchmode and one
    with a transformer and DC-DC converter.
    -Adding caps on the output of the powersupply, including plastic film and ceramic ones.

    -Using and input filter in front of the powersupply (230v side), not sure what the filter is called, metal can with caps and inducters inside.


    Nothing helps.

    Any ideas ?
  • Longbow
    Badcaps Veteran
    • Jun 2011
    • 623
    • USA

    #2
    Re: Noise problems

    If possible, a schematic of your project would be interesting. The problem appears to be line voltage fluctuation, rather than rf interference. Possibly the chip is being reset when other appliances are switched on.
    Is it plugged in?

    Comment

    • Th3_uN1Qu3
      Believe in
      • Jul 2010
      • 6031
      • Romania

      #3
      Re: Noise problems

      If the power supply is regulated the problem is not line voltage fluctuation. It COULD however be a bad ground in the house wiring, which is a pretty serious issue.

      If you run the project on batteries and it behaves, then you definitely have a grounding issue.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

      Comment

      • Rob Northen
        Senior Member
        • Jan 2010
        • 137
        • Denmark

        #4
        Re: Noise problems

        Its not a grounding problem or line voltage fluctuation, I'am a electrican myself and made the house wiring. When installed, ground was checked ok.
        I'am getting more into its the cabel between the processor board and the display, its about 60cm long..

        Comment

        • Th3_uN1Qu3
          Believe in
          • Jul 2010
          • 6031
          • Romania

          #5
          Re: Noise problems

          Maybe you need more bypass caps then?
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment

          • joshnz
            Badcaps Veteran
            • Feb 2011
            • 969
            • New Zealand

            #6
            Re: Noise problems

            Originally posted by Rob Northen
            Its not a grounding problem or line voltage fluctuation, I'am a electrican myself and made the house wiring. When installed, ground was checked ok.
            I'am getting more into its the cabel between the processor board and the display, its about 60cm long..
            is the cable shielded? I guess not I have had some weird thing's happen with my projects all related to interference or cross-talk.
            My pc
            CPU : AMD PHENOM II x4 @ 3.5Ghz
            MB : ASUS M4A89TD PRO USB3
            RAM : Kingston ValueRAM 16gb DDR3
            PSU : Cooler Master 850W Silent Pro
            GPU : ATI Radeon HD 6850

            Comment

            • Rob Northen
              Senior Member
              • Jan 2010
              • 137
              • Denmark

              #7
              Re: Noise problems

              Problem solved, after putting pull-up resistors on unused digital pins on MCU...

              Comment

              • Longbow
                Badcaps Veteran
                • Jun 2011
                • 623
                • USA

                #8
                Re: Noise problems

                Thanks for reporting back. Terminating all unused inputs on IC's, especially CMOS, is SOP because of their extremely high impedance. I came across a lot of equipment that had simple mechanical switches connected directly to a CMOS gate input. After a short while a tiny amount of oxidation on the switch, along with dust that settled on the switches would change the voltage on the input pins and cause unbelievable intermittent problems.
                Is it plugged in?

                Comment

                • ben7
                  Capaholic
                  • Jan 2011
                  • 4059
                  • USA

                  #9
                  Re: Noise problems

                  Ah, yes, you should always use pullup resistors on any unused pins of ICs, or else there will be problems!

                  -Ben
                  Muh-soggy-knee

                  Comment

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