USB flash drive extension cords are device specific?

  • Thread starter Thread starter John Doe
  • Start date Start date
J

John Doe

I have an inexpensive USB microscope. Weeks ago, it worked just
fine. Today, plugged it into a USB port through an extension that
came with a USB flash drive. The camera failed, so naturally the
camera or my Windows installation was suspect. I reverted to an
older copy of Windows to see if some installation had corrupted
something. Still the microscope did not work. Eventually, I tried
plugging the microscope directly into the USB port. It worked! Of
course I have read here about front USB ports somehow being
different than back USB ports, but that has not affected me. I
certainly would not think that a simple extension cord would have
some sort of different wiring (or resistance?). Go figure.
 
John Doe said:
I have an inexpensive USB microscope. Weeks ago, it worked just
fine. Today, plugged it into a USB port through an extension that
came with a USB flash drive. The camera failed, so naturally the
camera or my Windows installation was suspect. I reverted to an
older copy of Windows to see if some installation had corrupted
something. Still the microscope did not work. Eventually, I tried
plugging the microscope directly into the USB port. It worked! Of
course I have read here about front USB ports somehow being
different than back USB ports, but that has not affected me. I
certainly would not think that a simple extension cord would have
some sort of different wiring (or resistance?). Go figure.
Click to expand...

Voltages over USB can drop enough with the addition of longer run cable,
especially if they are cheap quality. Add to this the cabling from mobo
header to external USB ports and it can be enough to make the difference
between the device functioning or not. This can be compounded by additional
USB devices attached drawing the current down and cheap quality or under
specced PSUs.
 
BigH2K said:
Voltages over USB can drop enough with the addition of longer
run cable, especially if they are cheap quality
Click to expand...

Or maybe some USB flash drive extension cables were intended only
for USB flash drives, and somehow the design cut corners.
Resistance/power related problems are difficult to believe given
the device cable is 8 feet long and the extension is only 1 foot
long. I would expect intermittent failure, this one either works
or fails, the microscope is listed as a failed USB device.
Eventually maybe I will get around to testing it further.
 
Back
Top