USB isolator not working (I think)!

Discussion in 'The Projects Forum' started by electrophile, Jun 13, 2016.

  1. electrophile

    Thread Starter Member

    Aug 30, 2013
    I built an USB isolator (based on Analog's ADuM4160 and ADuM5000) to isolate my computer from a TI Launchpad board that will measure stepped down AC voltages and currents. I followed Adafruit's schematic and PCB layout for their version of the build, but I'm not sure this is working. Attached here is a quick video showing what happens when I plug it in the PC's USB port. The USB mini port (top left) is plugged into the PC and the USB A (lower right) is where the Launchpad is plugged in. The Launchpad does not turn on btw. Can anyone help? Oh and I should mention that the resistors on the data lines are shown as 24R on the Adafruit's design but I've used 22R. Would that make a difference?

    EDIT: Did some more testing. With no devices connected if I plug in a separate 5V supply on the USB mini side (PC side) the LED is a steady ON. I connected the Launchpad on the other end and it now powers up. When I now plug in the USB mini in the PC's USB port, Windows does not show a USB not recognized anymore but neither does it show a connected port. When I attempt to write to the Launchpad, I see a 'could not open port' message in the IDE.
    Last edited: Jun 13, 2016
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
    The circuit says those 24 ohm resistors should be 1%. Using 22 Ohm instead is over 8% out. I don't know whether that's got anything to do with your problem though.