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Mobile phone chargers

Discussion in 'General Electronics Discussion' started by Martaine2005, May 16, 2015.

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  1. Martaine2005


    May 12, 2015
    Hi all, what is the difference in Mobile phone chargers and power adapters?
    My old LG phone chargers label says ' travel adapter. input 100/240v , output 5.1v 0.7a.

    And so do all my other chargers and adapters allbeit different outputs.
    Can I JUST cut off the connectors and use them as ' adapters'?
    Or can they only be used for short term, like charging a phone?

    I realize that some chargers are completely different and pulse a higher voltage to the batteries. But the ones I am talking about are lighter (in weight) than the average power adapter.

    My question also applies to ' switching adapter ' and a traditional power adapter.
    Thank you in advance for any help. Martin.
  2. KJ6EAD


    Aug 13, 2011
    If the charger has a USB connector, then by convention it must output 5V at a minimum of 500mA. It may output a higher current but it may only do so in negotiation with the charged device. Most of them seem to have a 1A rating on the label but I've not needed more than 500mA for any of my projects.

    Chargers that have non-USB connectors may or may not be suitable as power supplies but since they can be obtained so inexpensively or even free, they're fun and useful to experiment with. You can load test them with a few power resistors, A 10Ω 10W resistor will load a 5V supply to 500mA. Two of the same resistor in parallel will load the supply to 1A. Use a DMM to measure the output voltage and current while loaded and look for ripple and switching noise with an oscilloscope if you have one.
  3. Martaine2005


    May 12, 2015
    Thanks KJ, I realise the usb types are 5v etc.
    But the other non-usb supplies are of different voltages and current ratings.
    For example, my old old Nokia charger says 3.7v @355ma.
    My old old Samsung charger says..AC DC adapter 5v @300ma.
    I guess that some are indeed adapters while the device has charging circuit onboard and others are chargers where the device does not have onboard charging circuit.
    How do I tell the difference without opening these pesky glued together adapter/chargers.
    I only have digital multi meters and no scope YET!!
  4. davenn

    davenn Moderator

    Sep 5, 2009
    Other than the USB ones ... all the rest are just standard plugpacks with the ratings written on them

    and when all said and done, even the USB ones could be used to supply a different device
    that requires 5V @ less than 1A
  5. KJ6EAD


    Aug 13, 2011
    The most difficult ones may have some intelligence inside that will prevent you from using them as a simple voltage supply without modification, modification that's only worth attempting for educational purposes.

    If you run across one that has a third wire, it may be a voltage sense line and you can either bond it to the positive lead at the load end or use it to adjust the output voltage.
  6. poor mystic

    poor mystic

    Apr 8, 2011
    You could put a slightly too-big load on the device and check for ripple, using your multimeter.

    Then again, hmmm. It can be quite a little project to set up a variable load.
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