# USB Laptop Light

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## Introduction: USB Laptop Light

Quick, easy and cheap way to make a USB laptop LED light. I made this one in about 20 minutes with spare parts. Great for presentation or just night time surfing.

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## Questions

why are you putting the green and red together??? what about the white and black? why didnt you put a resistor on your l.e.d. (why do you say it is 5 volt 30 mA)? nice project, except for a few... lot of questions i asked myself while you were building it... -gamer ps. please answer the many questions, because i dont understand half of the stuff about this video, and i know a lot about L.E.D.s and USB... thanks

All diodes (including LEDs) are CURRENT DEPENDENT devices. This means
that the current flowing through the device must be limited to the
specifications of the device (Too much current, the device will fail.
Too little current, the device will not conduct properly). The 30ma
rating on the package is the safe working current of the particular LED
chosen for this project, therefore, one needs to choose a resistor
soldered to the negative leg of the circuit to LIMIT the current flowing
through the LED in order to not have it burn out. As [mellink] explains
below, Ohm's law is used to calculate the value of resistor to limit
the current through the circuit to the proper value with the supplied
voltage.

can i help.
The LED when supplied with 5V and 30mA (3x10-3A) needs a resitor to stop the current burning out the LED.
Use V=IR to calculate the resitor value.
in this case:
V/I=R
5/(30*10-3) = 166.6 Ohms
So just go for a resistor near that and your safe.

hey i was wondering if i could damage anything on my laptop if i touched the positive and negative together.?prolonged or momentary i jus want to know before i damage anything.
thanks

+1

someone will have to explain the resistor to me....i dont quiet know why to use it. i can add that the laptop light 2.0 version. gamer - the ledinfo 5 volt 30 mA came off the package...was trying to tell folks what i used. from my research(not a lot) on usb cable the red and black are for the power the white and green are for data...when i used these it windows tried to discover my usb device and i only wanted power. plus these are the color combinations that worked, hope this helps will answer more if u want

im guess gonna have to make an instructable about the usage of a resistor, so everyone understands... when i try to get power from the usb port, i use the black as the gnd, and the red as the vcc (positive)... the data shouldnt be used, this is just giving the laptop a 1 on both data, and it wonders what that is supposed to mean... anyways... if it worked.

he meant the white and green wires of his led :)

he didn't touch the white and green data wires.

i had a 5volt 30mA LED they sell em at radio shack, they only need about a 1/4 watt 100ohm resister and they work fine