Urgent!! (i want to create a full wave rectifier}

Discussion in 'Homework Help' started by Halim.Akiki, Dec 29, 2014.

  1. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    1
    Hello
    I have a small project and i want to create a full wave rectifier. I drew the following circuit
    But i am having a negative result [​IMG][​IMG]
    Can anyone help me?
    The sine wave is :
    DC = 0 V
    AC = 16 V
    VOFF = 0 V
    VAMPL = 16 V
    FREQ = 60 Hz
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Can't see your images. If you are having problems, take a look at my blog entry here.
     
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  3. WBahn

    Moderator

    Mar 31, 2012
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    Post your (reasonably sized, like under 100KB) images as attachments to your post (use the Upload a File link at the bottom).
     
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  4. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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  5. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    Are they clear now?
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Of course you will get negative voltages. Turn your rectifiers around.
     
  7. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    1
    Are they clear now?
     
  8. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    1
    Thank you very much. I turned the rectifiers and the output turned out right. But when i added a resistor on the output i had the following result.
    Any suggestions? New results.png
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    Then increase the value of C1 to 1000μF.

    BTW, use a thread title better than Urgent!!
     
  10. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    1
    Thank you! I will use better titles.
     
  11. WBahn

    Moderator

    Mar 31, 2012
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    What size resistor did you use? How can we give good feedback if you don't give us the information?

    Since your output appears to be drooping from 14V down to 1V and that is being pulled from a 0.83uF cap, that means that you are pulling about 11uC of charge from it. Since that is being pulled out in 1/120th of a second, that's an average current of about 1.3mA. Since the average voltage is about 6.5V, I'm going to guess that you are using something like a 5kΩ resistor. Is that close?

    If you follow how I did that, then see if you can work backwards to find a good capacitor value to use to keep the droop (also known as ripple) below a desired value.
     
  12. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
    44
    1
    Man you're a genius!
     
  13. WBahn

    Moderator

    Mar 31, 2012
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    Wouldn't go anywhere near that far, that's for sure. But thanks anyway.

    What size resistor were you using?

    Did that help you size your capacitor better?

    What was the final result?
     
  14. Halim.Akiki

    Thread Starter Member

    Dec 29, 2014
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    I was u sing a 1K resistor. increasing the capacitor's size to 10mF made the result perfect.
     
  15. WBahn

    Moderator

    Mar 31, 2012
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    Yeah, in increase by a factor of 10,000 probably reduced your ripple voltage for that size load down to a millivolt or two. It will give you a pretty high inrush current, though.
     
  16. MrChips

    Moderator

    Oct 2, 2009
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    Please note that 1mF is 1000μF.
     
  17. WBahn

    Moderator

    Mar 31, 2012
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    Yes. So an increase from 0.83uF to 10mF is an increase by a factor of over 12,000.
     
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