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RE: [SeattleRobotics] Capacitor Voltage Rating ???

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  • Kevin Ross
    ... It should be noted, however, that the smaller the value, the larger the typical voltage is. For example, a 22pF monolithic ceramic capacitor in a through
    Message 1 of 6 , Jun 3 6:46 PM
      > -----Original Message-----
      > From: Ross Capon [mailto:robot@...]
      > Sent: Tuesday, June 03, 2003 12:53 PM
      > To: Pete Miles; seattlerobotics@yahoogroups.com
      > Subject: Re: [SeattleRobotics] Capacitor Voltage Rating ???
      >
      > bottom line
      > is: leave plenty of room over the max voltage in the
      > circuit, say a 16v
      > cap in an 8v circuit, but don't go overboard (500v in a 5v
      > circuit). of
      > course if you are using salvaged parts and space is not an issue, the
      > higher voltage will work just as well. --Tom

      It should be noted, however, that the smaller the value, the larger the
      typical voltage is. For example, a 22pF monolithic ceramic capacitor in a
      through hole package, is probably only available in 50, 100, or 200 volt.
      Functionally, in 5 volt circuit, they all work just fine. They are also all
      about the same physical size. This is basically true up to about 1uF in
      size. The pricing doesn't vary much either.

      The price differences show up in larger Electrolytic or Tantalum caps (>
      1uF).

      I usually settle in on a 25 or 35 volt part just to leave head room.

      Kevin
    • Randy Carter
      The voltage rating on a capacitor is the MAXIMUM voltage that can safely applied to the part. Exceeding this voltage will cause a failure as bad as exploding.
      Message 2 of 6 , Jun 4 9:08 AM
        The voltage rating on a capacitor is the MAXIMUM voltage that can
        safely applied to the part. Exceeding this voltage will cause a
        failure as bad as exploding.

        A capacitor is 2 conductive plates separated by a non conductor
        or dielectric. The capacitor's value is dependent on the size of
        the plates and the distance between them. To get a large
        capacitance in a small volume you make the dielectric as thin as
        possible. But this also reduces the amount of voltage that can
        be applied before it arcs through.

        In tantalum capacitors this results in a shorted component. In
        ceramic capacitors the damaged dielectric becomes a resistor that
        depending on the available current may catch fire. In
        electrolytic capacitors they either burst a seal and vent gas or
        if the overload is sever enough they explode sending the metal
        can skyward.


        > Pete Miles wrote:
        > Okay, here is one for you experts out there,
        >
        > What does the voltage rating on a capacitor mean?
        >
        > i.e. you can buy 16,35, 50, 500 volt versions of the same 1 microfarad
        > capacitor. So why are there different voltage ratings?
        >
        > And with this knowledge, does it matter which voltage rated capacitor I put
        > in a 5 volt circuit? (other than geometrical size).
        >
        > Pete
        >
        >
        >
        >
        > Visit the SRS Website at http://www.seattlerobotics.org
        >
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