Simple LED wiring question

[iamphantom]

I am working on a project where i want an LED (maybe 4 of them if theres enough power) to run off a USB cable i have stripped. The cable has four wires that are red, yellow, green and black. I know read when plugged into a computer has a 5V output. If my LED's have a forward voltage of 3-3.2 and a continuous current of 20ma how big of a resistor will i need? I have placed a diagram below to help. If at all possible I would like the USB to power 3-4 LED's but im not sure this is possible on 5V. Can someone check my diagram to see if it will work?

This is the link for the diagram:   http://iamphantom.co.cc/wiring%20diagram.jpg

[JP]

I am not an electronics expert by no means, but I have dabbled a bit here and there. I’m not sure if you would be able to reduce the voltage enough with that resistor or not. I’ve used rectifiers in the past to lower DC voltage, if it were me I’d buy 5v LED’s. It is even possible to get LED’s that can handle a voltage range, I have purchased one that can handle 6 to 12 volts so I would think that these days you would be able to get one in the 5 volt range.

Heat and high voltage is a problem for LED’s. Surges or heat will burn them out. You can use the information provided at http://www.wireityourself.com/ohms_law.html to figure out if your resistor is large enough to reduce the voltage, as far as the current it all depends on what your USB source voltage is capable of putting out and how much you are already using.