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Shorting a small capacitor with a switch

Discussion in 'Electronic Basics' started by Pimpom, Feb 9, 2013.

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  1. Pimpom

    Pimpom Guest

    I know it's not a good idea to short-circuit a charged
    capacitor, especially a large electrolytic. What about
    smaller caps - like a low voltage ceramic disc of 0.1uF or
    less? And if the shorting element is a low-power switch like
    one of those ubiquitous little square tactile microswitches,
    is the discharge energy enough to erode the contacts and
    shorten its life significantly?

    If it helps evaluate the situation, take as an example two
    cross-coupled NAND gates in the classic toggle switch
    configuration. As a bias to determine the initial state, say
    one input of one NAND element has the small cap to ground
    and is tied to Vdd via a resistor of ~100k. The microswitch
    parallels the capacitor. Is it advisable to insert a series
    resistor to limit the discharge current?
  2. Jamie

    Jamie Guest

    put an R in series with the switch...

    We short out large charged loads of 20Vk or more with a 10Watt 25k
    R and the crow bar contacts last a long time!

    When I say large I mean large cables of 10,000 feet of more with lots
    of dielectric charge using 20kV or more.

  3. Pimpom

    Pimpom Guest

    The video game controllers I know about usually use printed
    carbon contacts that are inherently resistive. I meant
    discrete switches with metal contacts.
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