Picture of How a USB Works: The inside of the cable
Hi all, My name is Dexter, I am 15 years of age and this is my first instructable. It will show you the inside of the USB cable. And will show you how to connect a light to it. NOTE: Do not directly connect an LED to a USB cable, use a resistor. I appologise for the poor quality of the photos.
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Step 1: Strip one end of the USB cable

Picture of Strip one end of the USB cable
Strip an end of the USB cable, remember to leave a USB port on one end, show the wires inside (with their coloured covers). The wires should be the same as in the photo below, the red wire = 5 Volts (+) and the black wire is the ground (-), for now ignore the other two wires I will hopefully make an instructable about them at a later stage. We will only use the black and red wires for now.

Step 2: Connecting the light

Picture of Connecting the light
OK firstly, I don't exactly know the type of light I use here, if you do please email me at . Connect the negative(-) wire of your light to the ground (black) wire of the USB cable and the positive (+) wire of the light to the red (5 volts) wire of the USB. Once the wires are connected nicely go to the next step.


Connect your USB cable into your USB port and the light should shine like in the photo below.
That concludes this tutorial. Hope this helps you in any way and that you have enjoyed my first Instructable.
Wind10001001 month ago

Can you adjust how much power is sent to the thing being powered over the USB cable?

Otherwise, does anyone know a cheap thing that can do that?

ctguy19556 months ago

I was wondering if I would be able to take the nice braided usb cable off of my
razer nostromo keypad, and switch it with the plastic usb cable from my
newly ordered razer Orbweaver Stealth that has not arrived yet ???

Thanks with your answer for this as I do hope its possible.

rcollins61 year ago

I need to make a very very important point! Especially because of knexpert1700.

A USB port can only handle 500mA of current, if more flows it may break the computer. Ohms law (V=i*R or i=V/R, i is current, R is resistance) tells you that if you have 5V, and connect some resistance to it, current will be voltage divided by that resistance.
LEDs have a very low effective resistance, and if you hook them up directly across a 5V supply without a resistor in-between (in series) you may draw more than 500mA (or simply burn the LED). If your computer doesnt have current protection, it could break the computer, or at least your USB port.
I would suggest putting a 100 ohm resistor in series to limit the current to around 25mA. This is an optimal current for an LED to function in most cases.

acolak1 year ago
can i do this with my wireless keyboard? i want to make it wired...there is 1 red and 3 black wires and one of the blac came from where the battery is.
Please help, I did this (on my own without this intructable) a few times and each time it breaks my usb ports on my computer. They either disable the data inputs or the electrical and the data. I dont want to break it again (I only have 2 left) so please help to see if I can fix this. :)
(removed by author or community request)
Well. Looking back while I was young, I did not know much. The USB suppose to output 5V with a limit current of 500mA ( just to be safe - it can be higher). Depend on how the circuit is actually build, over drawn current can have various effect - like rendering the port useless.

Read a bit about Ohm's law V=IR before you try it: Given the 5V and 500mA, you would like a resister that is at least 10 Ohm's without a light device. With a light device, the value for the resister can change depend on the lighting device you used - that 10 Ohm will protect the USB but may not be your lighting device - understand your lighting device will help you device a safe good circuit.
alpual2 years ago
simple and instructive. Thanks.
yet you dont tell us what resistor to use... not even a link to where they say what rated resistor for what voltage of LED.
Just use Ohm's Law V = IR
or R = V/I = 5/20e-3 (for 20mA diode)
so 250 Ohms
Seeing as electronics isn't an exact science use a 220 Ohm resistor or try using combinations of resistors. Don't be afraid of a little trial and error :)
llamma10104 years ago
 My cable is slightly different i have a lot of thin exposed metal wire along with ones you have the red is + the black is - and the exposed wires are ground
thats just another ground
Actually those wires are there to protect the Black, Red, White, and Green wires.
i thought it was connected to the metal casing of the USB connector?
A late addition to the conversation and hopefully you have already found the answer to your question, but for people finding this thread from a search, the exposed metal wire sounds like "Shielding". It is intended to reduce interference from other signals close by and should not normally be used as a "ground", or "return", though in some cases it may go to "Earth" which is NOT the same.
late, but not unread ;)
nice info, ty
Hanashimaru4 years ago
Thanks! This instructable actually cleared things up for me =D
324506allas5 years ago
thank you I am only 12 and this me a lot
I don't know why people post their age, and I didn't understood what you said :)
why so much negativity?
It is not negativism, it is just that, it seems dumb to do it.
"and this me a lot" Huh? And i guess that they are saying that they are young and foolish?
SterLuMan4 years ago
i think thats just a simple christmas light or a little light from a toy... and a great tutorial...
Hi i'm 14 years old and.. I already knew that , also like a million other people have been doing that as in connecting lights but what i am looking for right now is how to use the other green and white wires for your use
too bad you need a microcontroller...
Herminator6 years ago
is your name really Dexter, lol i love that show :D
JBizzle6 years ago
thats pretty cool. I dont believe I've ever seen inside a USB cable. lol
thanx =]
THE cable part was cool but the light not so much.
Wow its pritty cool to see such a young boy with electronics knowledge. Good one =)
gamer6 years ago
Second sentence ("It will how you the inside of the USB cable. ") doesn't make any sense, but other than that, cool! After reading that sentence for the 10th time, I realized that you probably meant "It will show you the inside of the USB cable".
Thanks for posting