capacitors - please help me to understand them better

Discussion in 'General Electronics Chat' started by Soogs, Jun 7, 2016.

  1. Soogs

    Thread Starter New Member

    Jun 7, 2016
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    Hi All,

    done a quick search but couldnt find the answer/s im looking for (here or on the wider web)

    lets say we have an input supply of 12v which i will step down to lets say 5v.
    please assume i know nothing about how any of these components work.

    if i were to use lets say a 35v xxx capacity. is the output voltage from the capacitor the desired 5v or 35v?
    or would the capacitor be placed before the regulator and there for output 12v?

    i hope this makes sense.

    Many thanks in advance,

    Soogs
     
  2. merts

    New Member

    Apr 1, 2016
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    I assume you're referring to DC volts.The output voltage would be the same as the input.
    However if it's at the output of a rectifier the output increases by Root 2.(1.414).
    5v would be approximately 6.1v
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,809
    834
    The figure of 35v is the rating of the capacitor. That is, it can be used in a circuit up to 35v.

    As merts said, whatever voltage is across its leads will be the voltage output. Also noted that the voltage source may affect the actual voltage being input. A rectified AC DC source may have an average voltage of 5v, but it peak voltage is higher.
     
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  4. Soogs

    Thread Starter New Member

    Jun 7, 2016
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    thank you very much for both your replys.

    my question has been answered and even learnt an extra :)

    I can already tell im going to love this place.

    Cheers

    Soogs
     
  5. Soogs

    Thread Starter New Member

    Jun 7, 2016
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    Sorry to post twice, couldnt find the edit option for my last post.

    I meant DC in my orginal post but Merts made me question the AC side of things.

    could someone please expand on this?

    assuming v in is AC in these 2 situations:
    ac before capacitor is lower than rated capacitor
    and
    ac is equal to rated capacitor.

    hope that made sense.

    Cheers

    Soogs
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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  7. Soogs

    Thread Starter New Member

    Jun 7, 2016
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  8. dl324

    Distinguished Member

    Mar 30, 2015
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    I don't know why so many distrust Wikipedia. I understand that it can be modified by anyone, but in all of the years I've referenced Wikipedia articles, I haven't found anything that looked like intentional misinformation.

    If you don't understand what you're reading, that probably means you're not ready to absorb the information and need to find more basic information and comprehend that first.
    I did a cursory scan and didn't see anything blatantly wrong. If you don't trust what you read, find a source you think you can trust (like text books).
     
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  9. wayneh

    Expert

    Sep 9, 2010
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    The voltage rating of the capacitor, which is often printed on the capacitor, has no bearing on the voltage developed on the pins of the capacitor. That is determined by the circuit which contains the capacitor. If the voltage rating is exceeded, there is a risk of permanent damage to the capacitor, leading to failure.

    I'm not sure what more you are asking. Perhaps you could post an example circuit you are trying to understand?
     
    etech7 likes this.
  10. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    A capacitor is like a water pressure tank. The voltage rating on a cap can compare to the pressure rating of a tank. The number of microfarads of a cap can compare to the volume of the tank. It all boils down to how much (energy/liquid) can it hold at what (voltage/pressure).
     
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  11. dl324

    Distinguished Member

    Mar 30, 2015
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    Some capacitors are polarized and some aren't. If you apply AC to a polarized capacitor, bad things can happen.

    It would be helpful for us (and you) if you asked more specific questions and provided more details. If you're at the "don't know enough to ask intelligent questions" stage, come back when you are.
     
  12. Soogs

    Thread Starter New Member

    Jun 7, 2016
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    thanks again for the replies.

    at this stage im just gathering some missing information.

    i have some ideas in my head but im not at a stage where i can draw diagrams that will make sense to you intelligent/educated people.

    i guess my first project is to convert a PC PSU into a bench supply (hopefully a variable volt unit). (or a 24v psu and use various components to achieve a varied stable output)

    i dont have much time on my hands to self eduacate. i have spent the spare time i have over the last 2 weeks trying to learn basic componenets and how they work and where to use them.

    capacitors simply did not filter well into my brain. the posts in this thread have been very helpful but it seems im still in well over my head when it comes to this.

    (edit: i will read the wiki pages when i have some more time and feeling a little fresher)

    thanks again.

    Soogs
     
  13. prof328

    New Member

    Apr 15, 2016
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    A word of caution if you are using a capacitor with a voltage rating it should be at least twice the voltage it is likely to see in your circuit.
    If it is a five volt circuit the capacitor should be rated for at least 10 volts, it wont matter if it's rated higher say sixteen volts.
     
  14. WBahn

    Moderator

    Mar 31, 2012
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    For technical information, Wikipedia is a quite good and reliable source of information. Some university actually looked at the quality of information on Wikipedia and Encyclopedia Britannica and found that, for technical and objective content, Wikipedia was far more accurate and up to date. Now, for subjective and controversial topics, Wikipedia can (not necessarily will) be a cesspool.
     
  15. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    You could also take a look at the links given on this page of the EDUCYPEDIA:
    Capacitors

    There you will find mainly links to universities and manufacturers.

    Bertus
     
  16. Sinus23

    Member

    Sep 7, 2013
    161
    409
    My experience as well. It is almost like us technical/scientific people don't like misinformation or something...;)
     
  17. BR-549

    Well-Known Member

    Sep 22, 2013
    1,995
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    You have to be willing to read and study a lot, to be able to understand a little.
     
  18. wayneh

    Expert

    Sep 9, 2010
    12,125
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    And when you become truly enlightened, you'll realize how ignorant you are once again.
     
  19. bug13

    Well-Known Member

    Feb 13, 2012
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    It's so true! I have that experience many time!!
     
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