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500 ma universal adapter OK for a 300ma device ?

Discussion in 'General Electronics' started by cd, Nov 15, 2003.

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  1. cd

    cd Guest

    I am want to get a universal AC adapter for several items I have around the
    house. The one I am looking at has a current rating of 500ma.

    One of the main items I want to use it on is a portable MP3/radio unit. But
    it specs that the adapter that is an accessory item for it is rated at
    300ma. Would the 500ma universal adapter I am interested in pump out too
    much wattage ? The unit normally uses 2 AAA batteries.

  2. Ken Taylor

    Ken Taylor Guest

    No, it's ok.

  3. Rich Webb

    Rich Webb Guest

    It will only deliver as much current as the load calls for. If it was a
    "real" regulated power supply, then it could have a much higher amperage
    rating and still be OK to use.

    The problem with the little wall-wart adapters is that they are
    generally pretty simple / cheap. (Which is not a bad thing; cheap is
    good.) However, their output voltage does depend somewhat on the load
    that they are presented with. If it's too far below the rated load then
    the voltage they deliver may sit at a level that's out of spec high for
    the downstream components.

    Using a 500 mA rated wart on a 300 mA rated load, you're probably OK.
    Might want to check the terminal voltage while it's running. If it seems
    too high (as in: your set the universal to 6 V but the voltmeter shows
    it at 9 V) then it's probably OK to drop down a tap to, say, the "4.5 V"
    setting if that produces a better match with the device that it's
  4. As long as the voltage output is correct for your unit it is okay.
    Infact a higher amperage rated unit will run cooler and probably last
    longer. A device will pull the amperage it requires.

    Just take note that the voltage output is correct for whatever device
    you want to use with a supply.

    Jerry Greenberg
  5. cd

    cd Guest

    Thanks to everyone for their help!
    Sincerely -
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