I attached split the end of a USB wire and attached a switch. When I press the switch, I measure 5V from the port, but am only measuring 33mA. Why am I getting only 33mA instead of 100mA?

  • 1
    \$\begingroup\$ What is the other end of the USB cable plugged into? \$\endgroup\$ – pingswept Oct 30 '10 at 6:34
  • \$\begingroup\$ It's connected to the multimeter. \$\endgroup\$ – 200ok404notfound Oct 30 '10 at 16:32

There is a decent chance that the computer is detecting a short and limiting the current back.

As pingswept said,

try a 50 ohm resistor

This will stop the computer from thinking there is broken hardware connected.

  • 4
    \$\begingroup\$ I think Kortuk is on the right track. Try putting a 5 V / 0.1 A = 50 ohm resistor in series with the switch. \$\endgroup\$ – pingswept Oct 30 '10 at 6:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.