How to ground switching power supply?

Discussion in 'General Electronics Chat' started by booboo, May 28, 2015.

  1. booboo

    Thread Starter Member

    Apr 25, 2015
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    I have one of this 24V 5A Switching Power Supply and want to ground it but I don't know how to do it because none of wall-socks at my home have ground(they just have L and N). an image of my supply:

    [​IMG]
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    See the circled symbol between N and -V, that is the supply earth connection.
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The supply will work fine without an earth ground connection, but it might radiate more noise. The earth ground connection goes to the supply case, and is there for safety reasons. Do not connect it to the Neutral.

    ak
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    You ground the unit using a length of wire from the point R!f@@ indicated to an electrical ground. Since your house doesn't seem to have such available you would need to create one, typically by banging an 8 foot rod into the earth itself. A licensed electrician could do this work while upgrading your house wiring.

    However, since everything else in your home seems to work just fine do what those devices do: insulate your final device in a nnon-conductive cover and keep all the dangerous voltages inside so they cannot be touched.
     
  5. booboo

    Thread Starter Member

    Apr 25, 2015
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    But I didn't say where is the supply earth connection.

    Thanks guys.
    Isn't there anyway to do it unreal? (I mean for example with a circuit or etc)
     
  6. booboo

    Thread Starter Member

    Apr 25, 2015
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    Why?
     
  7. R!f@@

    AAC Fanatic!

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    There is no unreal way to do it.
    Earth connection is used for safety reasons.

    I do not understand why you do not have earth connections. What country do you live in ?
     
  8. AnalogKid

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    Rifaa - there are millions of homes in the US that still have 2-wire AC outlets left over from when they were built.

    booboo - Since you have non-polarized AC outlets, either Line or Neutral can be on either wire depending on how it is plugged in. If you connect the GND to Neutral at the supply, and flip over the plug at the wall, the Line now is connected to the external case. The supply will work fine, but touching the case can kill you.

    ak
     
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  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It should also be noted that there are at least half a dozen devices on those units connected from the power lines and DC side to the case, suppression capacitors etc.
    Also one identical looking unit I opened up had the internal main fuse on the Neutral marked side.
    Max.
     
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
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    How? If he has no earth grounding system in his house and no common line connections to any type of earth ground which was a common design of the old two wire home wiring systems there is no way for his body to complete a circuit.
     
  11. ErnieM

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    Apr 24, 2011
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    And you are willing to risk someone's life on that statement?

    I assume booboo has a bathroom and a kitchen. Both have excellent earth ground in several places.

    Other paths may also exist.
     
  12. AnalogKid

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    Like that big damp concrete slab on the basement floor. But wait, there's less.

    Without telling anyone to do anything, I suggest that IF tcmhech were to put on rubber boots, stand on a plastic milk crate, insert a screwdriver blade into the Line side of any AC outlet, and grip the shaft, we would have what is called a teachable moment as he was knocked off that perfectly insulated perch.

    ak
     
  13. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I'm always willing to risk other peoples anything for the betterment of science! (Or personal entertainment.) :D
     
  14. cmartinez

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    Jan 17, 2007
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    I'd seriously consider checking for continuity between the L and Gnd terminals with an MM, just in case... of course I'm 99.999% sure that there won't be any, since that looks like a very formal, professionally made power supply... but I'd just check it anyway, just in case... a 0.001% case, to be precise.
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
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    There are almost certainly safety issues with leaving out the earth connection.

    What I'd reccomend is an earth stake driven into the ground under a convenient window. How to make a good earth is fully described in various ARRL and RSGB publications.

    Used to be that the cold water main was a convenient earth connection (but NEVER gas pipes!) in almost any house, youd find numerous places where earth straps were clamped onto water pipes. These days most water mains come in through plastic pipes, so its no longer a safe bet for earthing.
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    'Professionally' made in China?;)

    On one site I am moderator on, a company was advertising their Chinese made power supply units that had 120v plugs to source various switched 120v AC devices, the problem was they were the type that is used on PC power supplies as a male receptacle, in this case they were outlets!
    They pulled them when I reported it.

    [​IMG]
    Max.
     
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  17. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Oh my... well, yes of course you're right... there are chinese products, and then there are Chinese products.
     
  18. booboo

    Thread Starter Member

    Apr 25, 2015
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    Thanks guys for reply and sorry for delay.
    What about to connect the ground to the -V (not N)?
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As these power supplies are essentially galvanically isolated, generally you can earth ground the DC -ve side if required.
    Max.
     
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