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Re: [k8000] Re: Electrical interference

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  • Joris Struyve
    Hi, ... Since the IO circuit is separated from the rest of the k8000 card, I think the pull down resistor must be connected to the minus of separated IO
    Message 1 of 43 , Feb 1, 2004
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      Hi,


      > It does make a difference.
      > The IO channel has a opto coupler.
      > The minus of the IO channel is electricaly not connected to the minus or gnd
      > of the rest of the k8000.
      Since the IO circuit is separated from the rest of the k8000 card, I
      think the pull down resistor must be connected to the minus of separated
      IO circuit. We must reduce the voltage over the IO.


      --
      Kind regards,
      #####################
      Joris Struyve
      #####################
    • Richard Morrow
      Yeah you got it. Sometimes curcuit run on dual polarity supplys. For example an LM741 OpAmp needs a +9V and -9V to work. This can be done by connecting two 9V
      Message 43 of 43 , Mar 12, 2004
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        Yeah you got it.
        Sometimes curcuit run on dual polarity supplys. For example an LM741 OpAmp
        needs a +9V and -9V to work. This can be done by connecting two 9V batteries
        in series. The un connected +ve teminal is now +9V the -ve is -9V, and the
        connection between the 2 batts is ground or 0V.

        -9 GND +9
        o-----------00-------------o

        If u put the black wire of your meter on the GND point you should read -9
        and +9 when you put the red wire on the other points.


        I think Gunther mean just dont put your shield on the -ve end.
        When just running on 1 batt the -ve terminal is really 0V or GND, like u
        said. :)

        Grounding sometimes works better if u connect to a large metal object (eg
        the chassis of a robot)
        but this can also bring in other problems if you are not careful.


        Cheers, RIch

        >From: hihihi <hihihi@...>
        >Reply-To: k8000@yahoogroups.com
        >To: k8000@yahoogroups.com
        >Subject: Re: [k8000] Electrical interference
        >Date: Fri, 12 Mar 2004 14:15:26 +0100
        >
        >On Wednesday 21 January 2004 21:49, Gunther COPPENS wrote:
        > > Gents, Ladies,
        > >
        > > Any shielding of a shielded cable MUST be connected to EARTH-terminal
        >and
        > > NOT the minus of the voltage source.
        > >
        > > Otherwise shielding does not take place and interference passes the
        > > (mostly) aluminium shielding.
        >
        >This one is still bugging me.
        >
        >A long time ago i played around with building audio circuits.
        >Like amplifiers.
        >I did not ground these to the real earth.
        >I connected the shielding to the minus or 0 in case of a +X volt/ zero/ -X
        >volt power supply.
        >The result was no interference like noise or the 50 hertz buzz..
        >
        >So, to at least a certain level, you do not need to ground to real earth to
        >make shielding work.
        >
        >Part of the role of real earth, as i understand it, is safety.
        >Take a washing machine.
        >It has to be grounded for safety.
        >Suppose the mains wire comes lose inside the machine.
        >And touches the casing of the washingmachine.
        >When a human then touches a ungrounded casing he gets a shock.
        >But because the casing is grounded the current goes trough the easier
        >route,
        >the ground connection.
        >And not, or less through the human.
        >Or something like this..
        >
        >

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