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IC 555

Discussion in 'General Electronics Discussion' started by vick5821, Sep 4, 2012.

  1. vick5821

    vick5821

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    Jan 22, 2012
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    They'll probably be fine.

    Don't use them in life support applications though :)
     
  3. vick5821

    vick5821

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    Jan 22, 2012
    Just normal circuit will do :)
     
  4. vick5821

    vick5821

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    Jan 22, 2012
    [​IMG]

    Is it by using 10uF capacitor is enough ? Or I do not have any capacitor there is ok too ?
     
  5. davenn

    davenn Moderator

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    1,745
    Sep 5, 2009
    10uF on the input is probably too small unless you are only drawing a few 10's of mA
    it should really be ~ 1000uF if there's any chance the regulator IC is going to be supplying 500mA or more
    For stability from oscillations its standard practice to use 0.1uF (100nF) caps on the input and output in parallel with C1 and C2

    Dave
     
  6. vick5821

    vick5821

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    Jan 22, 2012
    Oh no, I bought 50 pcs for the 10uF cap..><
     
  7. davenn

    davenn Moderator

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    the 10uF are ideal for the output of the regulator ... ie. C2
    its just C1 that needs to be increased

    I should really qualify that ..... you havent said where the input to the regulator is coming from ?
    is it a battery ? or a transformer and rectifier ?
    If a battery, then you would get away with 10uF caps,just make sure they are rated well above the
    input DC voltage

    Dave
     
  8. vick5821

    vick5821

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    Jan 22, 2012
    Is it critical ? Then I need to buy 1000uF :)

    Thank you
     
  9. vick5821

    vick5821

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    Jan 22, 2012
    Yes, the input source from 9V battery :) Or sometimes from an adapter with 18V :)
     
  10. davenn

    davenn Moderator

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    1,745
    Sep 5, 2009
    ok then something from 10uF to 100uF would be ok
    note my other comment about the use of 0.1uF caps on the input and output of the reg chip

    D
     
  11. davenn

    davenn Moderator

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    Sep 5, 2009
    The importance of a larger value smoothing cap becomes apparent when the regulator is being driven from a DC supply derived from AC mains via a transformer and bridge rectifier.
    In this case the AC ripple voltage can be significant and gets worse as the current drawn rises.

    Dave
     
  12. vick5821

    vick5821

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    Jan 22, 2012
    Oh, means I have to use 4 cap ? 2 on the input and 2 on the output ??
     
  13. davenn

    davenn Moderator

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    1,745
    Sep 5, 2009
    yes a say 10uF and a 0.1uF on both the input and outputs


    D
     
  14. vick5821

    vick5821

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    Jan 22, 2012
    Okay. Thank you :) This is for stability purpose. But for small application I think I do not need the 0.1uF ?
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, the 0.1uF really should always be there. Read the datasheets for more information.

    The larger capacitor (10uF) especially on the input, would need to be increased if you intent to draw more current. A simple rule of thumb is 1mA per uF
     
  16. vick5821

    vick5821

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    Jan 22, 2012
    Okay! Then I should experiment with it first . Thanks for the info :)

    datasheet for voltage regulator ?
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yep...
     
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