wall charger and pc USB current>500ma

Discussion in 'General Electronics Chat' started by z4pped, Apr 11, 2011.

  1. z4pped

    Thread Starter New Member

    Jul 9, 2010
    does anyone know what happens when you put a load that that increases the current above 500ma on pc will do? and what if anything shorting the data pins do?

    also same question for a wall charger, specifically one with a stepdown transformer and rectifier for 5v @ 1A output.

    ie. if i put a 2.5ohm load on both of these the circuit would want 2A across the load, any information would be appreciated.
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    Unless the USB device asks for more than 100mA most USB ports will shutdown at 200mA. There are drivers by Gigabyte & ASUS that allow about 2A from compatible motherboards.
  3. z4pped

    Thread Starter New Member

    Jul 9, 2010
    Thanks blueroom for the reply. Although, thats not all the information I was looking for.

    let me reiterate.

    All these questions are for a 2ohm load

    1. With a 2ohm load over a usb.. I still dont understand, what happens. Does the voltage of the usb drop from 5v to whatever produces 100mA over the load? I have tested it on my desktop and laptop and my port does not shut down, but I cant get to the load to measure anything.

    2. also if the data pins arent in use, should they be shorted?

    3. what will happen if you try to pull 2amps out of a 5v @ 1A usb wall charger? Do they have a safety circuit that will shut it off? In the case that it doesnt, I assume it will still do something... what happens as far as the load currents and voltages?
    Last edited: Apr 11, 2011
  4. mjhilger


    Feb 28, 2011
    As Blueroom indicated, the specs call for the driver in a computer to shut down with more than the anticipated load. The software allows you to reset, but like a circuit breaker in your home if it is still too much current, it will shut off again.

    As for wall supplies as chargers, I think you are in pot luck category! Name brand supplies will probably fold under and only supply a very low current or shut off completely. Low cost supplies as you might purchase off ebay, might do really bad things.