220 Volts to 15 Volts Capacitor Resistor circuit

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Discussion in 'The Projects Forum' started by RodneyB, Sep 19, 2013.

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  1. Sep 19, 2013 #1
    RodneyB

    Thread Starter Well-Known Member

    Apr 28, 2012
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    I don't know what the name of the circuit is but using a capacitor and resistor the voltage can be dropped to a lower required voltage and then rectified. I am aware of the draw backs but from an economic point of view this just may be the practical route.

    I would Like to know how to calculate the components to build the above at 220 Volts to 15 Volts DC.

    Many thanks

    Rodney
     
    #1 Reply
  2. Sep 19, 2013 #2
    mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    transformerless power supplies are against the rules of this forum for safety reasons..

    how many amps do you need.. you can get 100-240AC to 15V power supplies for as little as $10-15
     
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  3. Sep 19, 2013 #3
    RodneyB

    Thread Starter Well-Known Member

    Apr 28, 2012
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    Sorry I didn't even think before I posted. I want 200 mA I will look at a small power supply like that. Again my apologies
     
    #3 Reply
  4. Sep 19, 2013 #4
    mcgyvr

    AAC Fanatic!

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    #4 Reply
  5. Sep 19, 2013 #5
    wmodavis

    Well-Known Member

    Oct 23, 2010
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    Use ohms law.

    The capacitor has impedance at the frequency used that can be calculated using standard equation for capacitive reactance.

    A voltage divider circuit with that capacitive reactance and the resistor in series can be used to reduce the voltage.
     
    #5 Reply
  6. Sep 19, 2013 #6
    wayneh

    Expert

    Sep 9, 2010
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    Not on this forum, it can't. ;) Isolation required to stay within terms of service.
     
    #6 Reply
  7. Sep 19, 2013 #7
    mcgyvr

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    If one knew how to do it properly and safely they wouldn't have to ask the question here.
     
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  8. Sep 19, 2013 #8
    wmodavis

    Well-Known Member

    Oct 23, 2010
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    Yes it can. It is a technical fact that can be done. I'm not the police just a humble technical person answering a question. My job is to answer questions if I so desire to not to pass judgment on what you may consider verboten for some reason. Your job, if you decide to accept it is to lock the thread if you feel that is the thing to do. The thread was not locked when I responded with some technical facts you seem to want to deny.

    Well its your turf so do your thing.
     
    #8 Reply
  9. Sep 19, 2013 #9
    wmodavis

    Well-Known Member

    Oct 23, 2010
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    If one knew all about electronics he wouldn't have to ask the question here. Right? What are you here for?
     
    #9 Reply
  10. Sep 19, 2013 #10
    mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    The point is that this site has rules.. Their rules do not allow discussion of transformerless power supplies for safety reasons.. Just because a moderator has not come along yet does not mean you should keep talking about it.

    As a forum member you should respect the rules of the forum or find another one.
     
    #10 Reply
  11. Sep 19, 2013 #11
    Georacer

    Moderator

    Nov 25, 2009
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    It seems unfair to close a thread where the OP doesn't really know what circuit he will use to do the rectification. So far the discussion was quite abstract, so I'll let it live for now.

    @RodneyB
    The suggestion of post #4 is a good one. For this kind of run-of-the-mill needs, a ready-made commercial solution is the cheapest and easiest.

    @wmodavis
    Intentional breaking of the Terms of Service, to which you agreed upon registering, isn't well-received, at least by me. Even if this isn't your thread, please discontinue this practice.
     
    #11 Reply
    RamaD and #12 like this.
  12. Sep 19, 2013 #12
    #12

    Expert

    Nov 30, 2010
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    Lucky Geo is on duty. Bill would have rapped your knuckles with a ruler.:D
     
    #12 Reply
  13. Sep 19, 2013 #13
    Wendy

    Moderator

    Mar 24, 2008
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    I thought strongly about moderating all of wmodavis replies, but decided to post this instead. The Terms of Service are for everyone, not just the OP. Since the OP has shown a willingness to consider a Wall Wart or some other isolating power supply I will not close this thread as is our usual policy. However, another moderator may feel differently, or if the subject of this conversation continues down the path I will close it.

    There really are ways to do things wrong, and to do things right. Let's keep it safe.

    Edit:

    Bill is always on duty, but sometimes it takes me a while. I missed the second part of the thread when posting the above.
     
    #13 Reply
  14. Sep 20, 2013 #14
    Georacer

    Moderator

    Nov 25, 2009
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    Bill is always watching, mostly from the shadows...
     
    #14 Reply
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