how to make two isolated 5V dc power supplies from single AC source

Discussion in 'General Electronics Chat' started by gadget_freak, Apr 27, 2016.

  1. gadget_freak

    Thread Starter New Member

    Apr 27, 2016
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    Hi, I recently came across this problem, while working with my arduino project where in it was necessary to have two isolated 5V dc power supplies. For that i used two 5V smps supplies. Now, the question is IS IT POSSIBLE TO HAVE SUCH TWO ISOLATED SUPPLY FROM SINGLE AC SOURCE? I am newbie so i don't have much idea if it is practically feasible. Will appreciate if you can help with this.
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    Yes, provided by isolated you mean the outputs of the supplies are isolated from the primary.

    Also, you might want to consider whether your chosen configuration will require one or both of the power supplies to be isolated from ground too.
     
  3. gadget_freak

    Thread Starter New Member

    Apr 27, 2016
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    Yes, 5V dc output should be isolated from the primary(230 VAC).

    And both 5v dc should have isolated ground with each other.
     
  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    That is a little bit more effort. One way is to start with a power transformer that has two identical secondaries (*not* a single center-tapped secondary). Each secondary can power a separate 5 V regulator (LM7805, LM317, etc.) with complete output and ground isolation.

    ak
     
  5. crutschow

    Expert

    Mar 14, 2008
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    If the two supplies are totally isolated, how you getting signals in and out between the two isolated circuits?
     
  6. gadget_freak

    Thread Starter New Member

    Apr 27, 2016
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  7. #12

    Expert

    Nov 30, 2010
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  8. ScottWang

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    Aug 23, 2012
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  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Nothing will work better and cost less than two USB power adapters. The device you linked to is designed for a specific application, not general-purpose projects. And it is very expensive. You can buy two USB chargers on ebay for $4 total.

    ak
     
  10. Ramussons

    Active Member

    May 3, 2013
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    " IS IT POSSIBLE TO HAVE SUCH TWO ISOLATED SUPPLY FROM SINGLE AC SOURCE? "

    Simply put, the answer is NO.
    From further discussions and clarifications, it seems that the above question did not convey the actual requirement.
     
  11. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    This is a basic approach, and needs refinements such as high frequency noise filters, transient protection, etc.
    EDIT: Corrected 7805 pinout.

    ak
    Dual-Iso-PS-1-c.gif
     
    Last edited: May 12, 2016
  12. gadget_freak

    Thread Starter New Member

    Apr 27, 2016
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    Thanks AK, your suggested schematic seems practically feasible. I wish if there exist some commercial product similar to this.
     
  13. hp1729

    Well-Known Member

    Nov 23, 2015
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    They both use the same ground. To clarify you may want to use a different ground symbol for each supply.
     
  14. ScottWang

    Moderator

    Aug 23, 2012
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    He already labeled as GND1 and GND2.
     
  15. AnalogKid

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    AND, the two symbols have different net name attributes, which are invisible except that they are printed on the schematic.

    ak
     
  16. hp1729

    Well-Known Member

    Nov 23, 2015
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    Ah, yes. I see.
     
  17. jsallas

    New Member

    May 17, 2016
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    Hello,

    Could you specify the output power you need? Do you require any efficiency/peak current?
    What application is this going to power?
    You want to buy something or assemble yourself?
     
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