Which way to connect a capacitor? - really basic question.

Discussion in 'General Electronics Chat' started by AgeingHippy, Dec 4, 2010.

  1. AgeingHippy

    Thread Starter New Member

    Nov 28, 2010
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    Hello All

    I need to connect a number of decoupling capacitors and am confused about which way to connect. My web search has turned up a lot of warnings but nothing to clarify to a complete noob.

    The negative (shorter) leg (cathode) on the capacitor. Does that connect to the GND or to the 5v / 12v side?

    Thanks
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did you read this thread with the attached documents:
    http://forum.allaboutcircuits.com/showthread.php?t=45583

    Small ceramic capacitors do not have a polarity, so they can be mounten either way.
    Electrolitc capacitors have markings for the minus (- connection) most times there is a coloured band on that side.
    You should take care that the polarity of the electrolitic capacitors is correct, otherwise you can damage the capacitor (sometimes even with a loud bang).

    For more information on the capacitors itself take a look at the capsite:
    http://my.execpc.com/~endlr/index.html

    Bertus
     
  3. AgeingHippy

    Thread Starter New Member

    Nov 28, 2010
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    I have Bertus, but it still does not answer my most basic question. Is the cathode (marked negative on the capacitor) connected on the ground side or the V++ side?

    I know the polarity has to be correct. Everyone and every web page states this, but does not say which way round is the correct polarity!!

    Can anyone simply answer the question please?
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    One important difference in polar capacitors is that electrolytic caps have the negative terminal marked, and tantalum caps mark the positive. Always be sure of the relative voltage differences of points with a capacitor between them so the smoke stays in the device.

    Old paper and foil caps had a mark at one end to indicate which lead attached to the outer wrap of foil. That was so you could tie that lead to ground and help suppress radiation of noise.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    Positive goes to positive, negative to negative.
     
  6. AgeingHippy

    Thread Starter New Member

    Nov 28, 2010
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    Hi Beenthere

    So to summarise in terms of my question - the cathode (negative marked leg) goes to Ground and the Anode possibly marked positive) goes to the 12v or 5v side?

    I know whomever first decided that electrical charge was a fluid decided it flowed one way but it (the electrons) actually flow the other way. This continually confuses me.

    Sorry guys. I know I am being really thick here, but I need this spelled out for me.
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    An electrolitic capacitor does have a + and a - connection.
    They are NOT called cathode and anode, as they do with diodes.
    The + connection goes to the point with the highest potential (VCC or +V)
    The - connection goes to the lower potential (GND)

    At an opamp you can have a negative powersupply.
    In that case the + goes to the higher potentioal (GND) and
    the - goes to the lower potential (VEE or -V).

    Bertus
     
  8. AgeingHippy

    Thread Starter New Member

    Nov 28, 2010
    16
    0
    Nice one

    Thanks bertus.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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