32.768kHz Crystal - Polarity?

Discussion in 'General Electronics Chat' started by demonGeek, Mar 25, 2009.

  1. demonGeek

    Thread Starter New Member

    Feb 27, 2009
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    I'm about to solder up a PCB containing this 32.768kHz Crystal and there's a square pad on one of the legs which is used elsewhere on the board to indicate polarity.

    Is the crystal is polarized and, if so, how do I tell?

    Many thanks.

    - Adam
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    I've never heard of a crystal having polarity, so I'm going to go out on a limb and say they aren't.
     
  3. demonGeek

    Thread Starter New Member

    Feb 27, 2009
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    0
    Thanks Bill - I didn't think it was polarized but it's the first time I've used one and I didn't want to guess wrong!

    - Adam
     
  4. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    I'v soldered a lot of crystals in place since 1980 and the only ones that are (sometimes) polarized are those in crystal filter circuits - but even then, they will have three legs! (There will usually be a dot or dimple at one end, this indicates polarity.) But these are not crystals to be used in an oscillator - they are being used as filters.
     
  5. steveb

    Senior Member

    Jul 3, 2008
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    If you hook a watch crystal up with reverse polarity, time will run backwards. :p
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    .taht wonk t'ndid I ?yllaeR
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Hooked a battery up backwards in a car once.

    Horn sucked, radio listened, headlamps cast shadows.... :rolleyes:
     
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