USB Power

Discussion in 'The Projects Forum' started by zac, Dec 18, 2008.

  1. zac

    Thread Starter New Member

    Dec 15, 2008
    I've got a thing going on at the moment, where I like to make USB powered things, but my problem is. Since USB is only 5v, would it be safe if I ran two usb cable and hooked them up in series to make 10v?

    Thanks, Zac.
  2. leftyretro

    Active Member

    Nov 25, 2008
    No, that won't work. All the USB ports on a PC get their voltage from the same PC system power supply and all the USB ports share a common ground terminal so there would be no way to series them up. However you could build or buy a small DC/DC converter to generate whatever voltage you wished. Keep in mind that USB 5 volt power is limited to 100ma per port, unless a USB device communicates to the system's USB controller requesting more current and then may be issued a maximum of 500ma per port. 1/2 watt of power is not much to work with, useful for slow charging of batteries at best.

  3. bertus


    Apr 5, 2008
  4. zac

    Thread Starter New Member

    Dec 15, 2008
    Alright thanks guys, I guess what I might do is get an old computer PSU and modify it into a homemade lab psu. I will cut all the un needed cords, and then use a potentiometer to be ale to adjust the voltage that gets outputted. I will use a spare terminal I have (you know the sort you find on the back of old speakers?) to be able to get power from it.

    Also, would connecting more 12v power cables from the psu together just result in more amperage? And is there any reason I would need more amperage output than what it would normally put out?