Why is this RC circuit not working?

Discussion in 'Homework Help' started by alpha_centaur, Sep 9, 2010.

  1. alpha_centaur

    Thread Starter New Member

    Sep 9, 2010
    5
    0
    Hello all!

    I am really stuck up here. I have made this circuit and want to measure the voltage across the capacitor. The voltage should gradually increase as the capacitor charges, and then become constant. But, I only get a constant voltage of 6V across the capacitor.

    Infact, I have to measure the time constant. I am doing a transient analysis, and when I plot the voltage, it just shows a straight line, and no rising trend.

    Please help!

    The circuit image can be seen at:

    http://img641.imageshack.us/img641/8897/rccircuit.jpg
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Thats going to rise pretty darn quick.

    Did you set your analysis start state with the cap at 0v?
     
    alpha_centaur likes this.
  3. alpha_centaur

    Thread Starter New Member

    Sep 9, 2010
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    Thanks for the quick reply.

    Can you please tell me how to do that ?
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    What software are you using?
     
  5. alpha_centaur

    Thread Starter New Member

    Sep 9, 2010
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    I am using PSPICE v9.1 Student Edition
     
  6. Ghar

    Active Member

    Mar 8, 2010
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    You're looking for the checkbox "skip the initial bias point calculation" under simulation settings.
     
  7. alpha_centaur

    Thread Starter New Member

    Sep 9, 2010
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    Thanks for replying.

    I managed to solve the problem by setting the initial condition of the capacitor to 0V.
     
  8. victorhugo289

    Member

    Aug 24, 2010
    49
    3
    Hello, I recommend you to use Spice2g6. I know nothing about version 9.1
    I think the reason you´re not getting any indication of increasing voltage is because it happens very fast, that capacitor is very small, you should use at least a 1000uF one.

    A yeah, I mean if you´re trying to measure the real circuit. In Spice theres no problem with time.
     
  9. alpha_centaur

    Thread Starter New Member

    Sep 9, 2010
    5
    0
    Thanks for replying.

    My problem has been solved by setting the initial condition of the capacitor to 0 V.

    Cheers!
     
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