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What power supply (amps) would run this plasma globe optimally?

  1. Jul 15, 2015 #1
    my 3inch plasma globe needs 5V 300mA dc supply...
    Can I use an adapter with 4.5V and 50mA output rating?
    If can't then what will happen if I still do use it?
     
  2. jcsd
  3. Jul 15, 2015 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    It most likely will not work. A 4.5V supply with a current rating of >=300mA might work, but an output current rating of only 50mA looks to be way too low.
     
  4. Jul 15, 2015 #3
    I have another adapter with 1A rating but its 12V....i suppose that will be too high??
     
  5. Jul 15, 2015 #4

    berkeman

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    Staff: Mentor

    Yeah, probably too high. Did the globe not come with a power adapter?
     
  6. Jul 15, 2015 #5
    actually it did... but with car adapter not with a usb or power plug adapter..
    I got it from ebay for 835 INR and the sales package details said nothing about it containg any adapter let alone specifying the type of adapter
     
  7. Jul 15, 2015 #6

    berkeman

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    Staff: Mentor

    When you plug it into your car, does the globe work?

    Also, can you measure the output voltage from the car adapter? If it's 12V (no down-regulation), then your 12V power adapter should be okay.
     
  8. Jul 16, 2015 #7

    meBigGuy

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    Gold Member

    1. You should not go above the rated input voltage. If that's 5V, (does it say that on the globe?) then absolutely do not go above it.

    2. You must be able to supply the 5V and the current specified. That is, when the globe draws 300ma, then the power source should still be 5V.
    An adapter with 50ma rating will likely not put out 5V with a globe attempting to use 300ma

    3. I find it hard to believe that a 5V 50ma power adapter even exists. Is it possible you are misreading it? 5V 500ma and 5V 1A are both very common.
    (I take it back --- I guess they exist)

    Just about any cellphone charger is 5V 450ma at least.
     
  9. Jul 16, 2015 #8
    You need 5V. You need at least 300mA. (You might be able to get by a little low on that if the design engineer over built the supply.) But more current will work.

    I seem to recall USB is 5V. I forget the current, but I think it will source 300 mA. So any USB supply should work.
     
  10. Jul 16, 2015 #9

    meBigGuy

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    Gold Member

    The USB specification is that if you do not enumerate at all you not supposed to draw more than 2.5ma. for any length of time.
    If you enumarate you and draw 100ma. You must not draw more than 100ma unless you enumerate and request higher power. Then you can draw 500ma.

    The specification is actually much more complicated than that, including a sub-threshold signalling protocol, but I won't go into that.

    Not all USB devices enforce this.
     
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