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Positive Ground

Discussion in 'General Electronics Discussion' started by inlineskater, Jun 16, 2012.

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  1. inlineskater

    inlineskater

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    Jun 15, 2012
    Hello

    For anybody working out in the field even at your bench. How common is a "positive ground". Please do not post a "Google answer or URL". I am asking based on actual users who work in the field are members of this forum. If you have ever worked with a "positive ground" what were the pros and cons?

    Thank you
     
  2. john monks

    john monks

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    Mar 9, 2012
    Not very common. I work on nim power supplies and products and that system uses positive and negative supplies. Transistor radios in the 1960's and 1970's typically used a positive ground. The only advantage as I see it is with PNP transistors positive ground circuits are easier to follow and sometimes a negative ground is complimented with a positive ground to prevent ground offset voltages. Many years ago cars with 6 volt batteries used a positive ground for reasons unknown to me. Why do you ask?
     
  3. Raven Luni

    Raven Luni

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    Oct 15, 2011
    A ground is simply a reference point and can be at any potential, for example a split rail supply for an amplifier has the ground half way between the positive and negative rails (also known as a virtual ground since the precise level has to be actively maintained). A positive or negative ground simple means that your reference point is one of the 2 supply rails and all other voltages in the circuit are relative to it.
     
  4. inlineskater

    inlineskater

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    Jun 15, 2012
    While out looking for an adapter for a family member I was told that I needed an adapter with a positive ground. And the sales guy said thats why its double the price. And see'ing in various circuits and such. I was curious to see how common it is.

    Thank you
     
  5. Raven Luni

    Raven Luni

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    Oct 15, 2011
    Vulcan mind melds dont seem to work over the internet so it will have to be an old fashioned ask: what kind of adapter? Mains adapter? Audio adapter? Logic adapter? Hose adapter? Bike pump adapter? There are so many....
     
  6. inlineskater

    inlineskater

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    Jun 15, 2012
    It was a Computer adapter. :)
     
  7. Raven Luni

    Raven Luni

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    Oct 15, 2011
    See above reply ('computer' represents a massive subset of adapter types).

    What I should have said is describe the adapter and its function in as much detail as you can.
     
  8. inlineskater

    inlineskater

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    Jun 15, 2012
    It was for a laptop - an adapter was purchased and I do not have any other details. I was more curious to how common it was.
     
  9. gorgon

    gorgon

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    Jun 6, 2011
    Most grounds are referenced to 0V, so when you say positive ground, the meaning is really that you have a negative supply voltage.

    Since a positive supply voltage is the norm, there are som issues connecting things together if you have both systems. If you have a single power supply, you can't connect them together with the same 0v reference, you'll need two powers.

    To anwer your question, a positive ground is not common at all. In addition to the things said, I can remember some english cars that had a positive ground, a very long time ago.

    TOK ;)
     
  10. CocaCola

    CocaCola

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    Apr 7, 2012
    Because it didn't matter at that time... :)

    The standardization to negative ground came to play as the cars became more and more electronic while including more and more electronic gadgets inside... Radios being a huge initial factor...
     
  11. Alchymist

    Alchymist

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    Apr 16, 2011
    Telco service uses positive ground systems....I think it's -48 volts as the supply voltage ...
     
  12. JMW

    JMW

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    Jan 30, 2012
    Positive ground cars eliminated much of the corrosion caused by electrolysis. Mack used it until the mid '70's. It prevented the cylinder liners from welding themselves to the block, making engine rebuilding easier. Accessories needed a positive ground converter. It was a DC to DC converter with a floating (ungrounded) power supply It made troubleshooting a bit difficult, I finally discovered just plugging the red meter lead into the ground jack and black into the hot and then going from there. Don't really know why the auto industry didn't go + ground. I don't like conspiracy theories, but planned obsolescence?
     
  13. john monks

    john monks

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    Mar 9, 2012
    A positive ground would cause the car body to deteriorate.
    A negative ground would cause the wire to deteriorate.
     
    Last edited: Jul 31, 2012
  14. gcb

    gcb

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    Mar 26, 2012
    because the + charge on the body would draw - charged O to the metal? or my uninformed guess is totally off?
     
  15. CocaCola

    CocaCola

    3,635
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    Apr 7, 2012
    I believe you will find a bunch of "hearsay" supporting both sides in regards to what rusted worse... Sure there is some science to support one or the other but I believe in the end you will find that it doesn't really matter all that much...
     
  16. john monks

    john monks

    693
    1
    Mar 9, 2012
    The positively charged ions is pushed away from the positive electrode and migrates towards the negative electrodes.
    The corresponding electrons migrate from the negative electrode to the positive electrode.

    This would be one good reason the telephone companies use positive ground, to keep their wires from deteriorating.
     
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