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Power Supply Help and Advice Sought!

Discussion in 'Electronic Basics' started by SME, Dec 30, 2003.

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  1. SME

    SME Guest

    Dear Group,

    I have schematic that I found on the web it was designed for US 120V mains.
    What
    do I need to do to convert it for UK 240V?

    Also the two capacitors C1,C2 200V 4700uf are very expensive is there anyway
    to get the same effect by using smaller cheaper ones ie in parallel or
    serial ?

    I attempted to draw the schematic with text characters but it looked like a
    mess!
    Please follow the link below to view the schematic.

    http://paragon.chill.net/

    Thanks For Your Help.
    Steve
     
  2. tempus fugit

    tempus fugit Guest

    What is it a power supply for? Looking at it, I can't see how it would
    deliver the voltages it's suggesting. Also, is that supposed to be connected
    to 350v at the top, or the voltage measured there?
     
  3. Chris Oates

    Chris Oates Guest

    I think he's trying to make a voltage doubler
    by copying the C values from a very low voltage
    circuit - C is massively too big
     
  4. SME

    SME Guest

    Yeah that's exactly what I am trying to achieve but I am beginning to think
    that maybe 350VDC is a little to large.
    I am also concerned with the hazard as believe it or not I do value my life!
    ;-)

    I have a thread running on sci.electronics.design that is a little more
    mature than this so it may be worth taking a look there!

    Thanks for your replies thus far...

    Steve.
     
  5. To convert your device from 120 to 240V operation you need to remove the
    connection between the 'central tap' of the 2 capacitors and NEUT, i.e. NEUT
    will only be connected to the rectifier, but no longer to the caps. That's
    all. The caps' central connection will no longer be used. This was a common
    design in AT power supplies some years ago, there was a 120/240V swich that
    allowed 120V operation when closed and 240V when open. Many nowadays' PS
    adjust themselves to the voltage automatically, but that's another story.
    The caps will be expensive indeed, but everything depends on whether you
    really need that thing to deliver 7.5A (or this like). If only 2A or so is
    needed, use smaller caps. Note that if the device is to be operated from
    ONLY 240V and does not need the ability to be switched back to 120V, you
    need only one cap (2.4mFx400V in this case). Values like 4.7mF (or even
    2.4mF at high voltages) are best obtained from multiple caps in parallel. In
    any case, could you please tell us what this is gonna be used in, it will
    make your situation a lot easier for us to analyze.

    Dimitrij
     
  6. Ross Mac

    Ross Mac Guest

    I agree with Chris, that's a typical voltage doubler circuit. If you want
    "that" circuit you will need a 2:1 stepdown xformer....An additional expen$e
    ! Have you tried electronic surplus? You might find a deal there on all the
    parts... Here is a place I use.... http://www.alltronics.com ... If you
    buy the caps there be sure to check the date codes. Call them with a parts
    list. The xformer will have to be around 2.5 to 3 KVA dependant on how much
    of that 20 amps you really need and make sure to fuse it. If you can't find
    the parts there try a google search...good luck on your project...Ross
     
  7. SME

    SME Guest

    Dimitrij thanks very much for your reply...

    Take a look at the following links this is where I got the schematic from
    but this was only a small part of it.
    This should explain what I am enquiring about better than I could here ;-)
    You may also wish to take a look at the group sci.electronics.design as
    there is a duplicate thread running there that has had a little more
    replies.

    http://dave.golfbuddys.com/hvguy/new/2500Wheater.htm
    http://dave.golfbuddys.com/hvguy/new/2500Wheater_2.htm

    Thanks Again,
    Steve.
     
  8. SME

    SME Guest

  9. Ross Mac

    Ross Mac Guest

    Cross post it next time!!
     
  10. SME

    SME Guest

    Sorry to sound a little dumb but is cross posting achieved by sending it to
    both groups at the same time?
    ie
    Newsgroups sci.electronics.basics;sci.electronics.design
    Regards
    Steve.
     
  11. Ross Mac

    Ross Mac Guest

    Yes...just post it to the groups you would like a response from...this way
    the posts go everyone and eliminates duplication.....Ross
     
  12. Ross Mac

    Ross Mac Guest

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