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What's the current supply of a USB? Answered

I want put 3 LED's and a flashdrive into another container, and have the LED's turn on when plugged in, but I'm not sure how to go about wiring up the LED's. What's the supply current that I should use to find the right resistor?

If a poorly made diagram gives you a better idea of what I'm talking about you're in luck!

I know USB gives 5 volts, but I don't know about the current.

And would any problems arise from three LED's and the drive plugged into one USB?



Best Answer 8 years ago

No more than 100mA without smarts in the box you plug in, so three LEDs you should be fine.


8 years ago

You have all the information you need. Now just apply Ohms Law -- V=IR to calculate the resistance. If you want to make it even easier, use led.linear1.org/led.wiz . You have the diagram exactly right, 3 different leds with different resistors on each. Be sure to change the V(f) for each led because each colour will draw different voltage. Most leds are happy with 15-25mA each. Tip: underdrive them (less mA) so they are not obnoxiously bright and use less power.