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How do I increase Voltage, USB extension cable is causing voltage drop.

Discussion in 'General Electronics Discussion' started by red913, May 18, 2015.

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  1. red913

    red913

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    Mar 22, 2013
    So my wife got me a USB extension cable to charge my phone, so I could sit in the center of the bed(it's a king) next to her when using the phone before bed. Cute idea and it seemed to work for awhile, but recently it's suffered such a voltage drop that the phone won't charge anymore on the extension cable.It will charge when just on the factory cable though. The app I got says without the cable, 3.7V, but with, 3.5. So is there a way to maintain the higher voltage? I'm still a novice in electronics, so not sure if there is anything I can do.

    My first thoughts were a capacitor, but that would only work for a very short while. The voltage never goes high enough to "recharge" the cap. I know transformers will increase or decrease voltage without affecting power...but do they make them for something as small as .2V?

    Not sure what other options there are...ideas would be appreciated. :)
     
  2. poor mystic

    poor mystic

    1,074
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    Apr 8, 2011
    :)
    Hi Red
    If a set-up that worked fine in the past no longer charges your phone, you'll need to test to find out what has changed.
    The candidates are the transformer and the extension cable.
    If the extension cable charges your phone from another transformer, your existing plug-pack might be faulty. Otherwise it's likely to be the extension cable.
    (It sounds more like the transformer to me but testing makes better sense than jumping to conclusions)
     
    davenn likes this.
  3. red913

    red913

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    Mar 22, 2013
    It's more likely the cable as I tried a different charger already and yielded the same result. But I'd still like to know, just for the sake of knowing, how would I go about increasing the voltage just a little bit?
     
  4. davenn

    davenn Moderator

    13,991
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    Sep 5, 2009
    You really don't want to increase the voltage on a USB lead .... very unwise
    you are sure to accidentally one day plug it into something that cannot handle the extra
    voltage and kill it

    sort out your cabling problems
     
    foTONICS likes this.
  5. poor mystic

    poor mystic

    1,074
    36
    Apr 8, 2011
    It sounds a lot easier than it is, to increase voltage. Reducing it's easy enough, like spending money... but increasing voltage usually means starting afresh.
    Anyway, I hope you noticed what Davenn said just above :)
     
    davenn likes this.
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Your software measurement of the voltage is also suspect.

    USB is 5V, if you were ever getting 3.7, the charger is broken. I'd imagine that the app is telling you the battery voltage.
     
    davenn likes this.
  7. red913

    red913

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    Mar 22, 2013
    It seems I'll have to start a new thread on increasing voltage because at this point it's just curiosity on how such a thing is done, regardless of the USB plug, yet I can't get a straight answer on how such a thing is done. I'm not going to modify the plug. That much is clear to me that it's not a good idea.

    ya, you're probably right. I was wondering the same thing myself about the 5V.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I recommend you get a cheap USB voltage/current monitor for a couple of dollars on eBay. You can compare the voltage before and after the extension cable.

    On the topic of how you might increase the voltage, a boost switchmode regulator could do it. However the problem is more likely to be either the extension cable or the charger. Fixing either of these using a boost regulator is akin to fitting springs to the seat of your car to fix a problem with the tyres or suspension.
     
  9. poor mystic

    poor mystic

    1,074
    36
    Apr 8, 2011

    OK, you need to know how to design a "power supply".
    There are lots of books and all, but the first thing you'll need to understand is a simple, unregulated supply, which will consist of a transformer, a rectifier, a capacitor, and a load.
    It's good to see the load as part of the power supply design.
    You'll start by specifying a load, which will mean you know how much current is wanted, and what voltage should be provided to drive the current through the load.
    But, you're right!
    Start a new thread, and let's see what we come up with!
    :)
    Mark
     
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