smd capacitor type to be used instead electrolytic capacitor

Discussion in 'General Electronics Chat' started by imraneesa, Jul 8, 2015.

  1. imraneesa

    Thread Starter Member

    Dec 18, 2014
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    4
    hello Sir,

    i am building a 555 circuit and i want to use surface mount components.
    The main capacitor that i have to use on pin 2 of 555 is 1uf. i normally use electrolytic capacitor but this time i need to use surface mount components. so i dont know which type of capacitor i have to use. tantalum or if i can use ceramic capacitor. please throw some light on this.
    The doubt arises becoz i know it should not be bipolar type. so ceramic smt capacitors we can use either way without any polarity problem.

    Also kindly give me a link in digikey pointing the type of capacitor that i can use.
    Thanking you in advance.
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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  3. imraneesa

    Thread Starter Member

    Dec 18, 2014
    189
    4
    Thank you Sir.
     
  4. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    5,178
    1,474
    A while ago, surface mount ceramic caps came under fire for cracking when a pc board is flexed during assembly or shipment. The industry responded with a "soft" package that has just a tiny amount of flex-ability built in. Make sure you get this feature.

    And by the way, there are excellent surface mount aluminum electrolytics if you need larger cap values in the future.

    ak
     
  5. Bordodynov

    Active Member

    May 20, 2015
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    Bad idea to use electrolytic capacitors in the circuit of timing. These capacitors have a leakage current is strongly dependent on temperature. In addition, they "desiccate". Manufacturers provide lifetime oxide capacitors.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    Why would you say that?

    The 1979 Signetics Applications Manual states that "Capacitor size has not proven to be a legitimate design criteria. Values ranging from picofards to greater than one thousand microfarads have been used succesfully."

    Low leakage caps are of course desireable, but some circuits don't require timing to be very precise.
     
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Note that polarity stripe on SMT cap. is the + side. No mark on seramic non polerised cap.
     
  8. dl324

    Distinguished Member

    Mar 30, 2015
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    The suggested cap has no stripe. The top of the can has a black mark on the negative side.
    smdElect.jpg
     
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