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power single LEDs with USB? Answered

I'm wanting to use some single 0603 LEDs here and there for a display.  I want each light to have its own power plug.  I'm figuring usb cables are a good way to do this (since I can power them by plugging into a hub, and retractable usb cables are cheap and handy).  If anybody has a better solution, I'm open to ideas.

My question is whether there's some way to use a single resistor with the hub, instead of needing to add a resistor to each usb cable?  I'm assuming no, but figured it doesn't hurt to ask.

Also, do I need different resistors depending on if it's usb, usb 2, or usb 3 hub/cables?

And finally, since I'm getting my 0603 LEDs from some pre-wired Christmas light strands (mostly white, but a few colored), I don't have exact specs.  Is there a general standard that I should use for calculating which resistor to use?  3volts and 20mA sound good?



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7 years ago

You need a resistor and each LED. The resistor value is based on the specs of the LED. Without knowing the specs of the LED you'll have to play around with them a bit. Get a bread board so you can plug in an LED and a 5V power supply. Then you can change out resistors till you find one that gives you the best brightness without blowing the LED or killing the power source. BTW don't experiment with any USB port tied to or getting power from a PC. Chances are a 100 to 300 ohm resistor is all you'll need with a single LED.