LED to usb cord help

alright, so i was just think one day...la la la...what about putting a led on a usb cord to tell when you are connected? sound dumb? shut up! jk

you guys looks really good with electronics.

o ya, i am new here.

ok, now, 2 questions, accualy 3. or maybe more.

1. which is the brightest LED here that runs at the most 5v.

http://www.radioshack.com/family/index.jsp?categoryId=2032298&cp=2032058.2032233

2. depending on which is the brightest, and how many volts it runs on, how many ohms would my resistor would need to be? (gimme a radioshack link)

3. this looks cool (this is a totally different issue)

http://www.radioshack.com/product/index.jsp?productId=2062601&cp=2032058.2032230.2032279&allCount=27&fbn=Type%2FIC-Analog&f=PAD%2FProduct+Type%2FIC-Analog&fbc=1&parentPage=family

is there a minimum voltage that has to go into it? and how do u set it to have it output the amount of voltage you want?

i want to hook up someway to charge my digi camera battery which is a 4.2 volt battery. probaly via usb whcih supplys a 5v. and i have another question but it is low priority, i will ask later.

Welcome to CPF!

If you can help it, I'd avoid buying at RadioShack... their stuff is overpriced.

If you want white, and the brightest possible, I'd look for Nichia CS 5mms, which take overdriving abuse well. In case you don't know, USB has I believe a 5v wire in the specs. You probably want at least 3v to power an LED.

Don't want to spoil your fun... but... http://www.thinkgeek.com/computing/accessories/7265/

there is a radioshack within a like 2 min walk from my house. so i want to get it from radioshack

In case you don't know, USB has I believe a 5v wire in the specs. You probably want at least 3v to power an LED.

ya i know that. i am asking what type of resistor would i need to down 5v to about 3?

and ya i know they make those things, i am kinda using that inspiration to build mine. mine will just be coming out of the wire.

You should know also, that there is a current limit of 200mA (0.2A) on most USB ports, so you'll need to keep the maximum battery charge current and LED current (as a combination) below that, or you might see the following on your computer screen:



When this message comes up, power to the USB port will be terminated.

eh no offense guys..but

how many ohms does my resistor have to be!

for a 2.1v to a 3 v led?

http://www.radioshack.com/product/i...032058.2032233.2032298&pg=2&parentPage=family

150 ohms for a 2.1 volt LED, and 100 ohms for a 3.0 volt LED; both driven at 20mA.

and lemme guess. i set it up like this

...

hold up, do resistors have + and - sides? i know led's do. the longer metal thing on the led is the positive one. so i hook one end of the resistor to the 5v lead, the other end to the positive thing of the led. the - led thing to the ground on the cable right?

techno nerd said:

hold up, do resistors have + and - sides?

Click to expand...

Nope.

techno nerd said:

so i hook one end of the resistor to the 5v lead, the other end to the positive thing of the led. the - led thing to the ground on the cable right?

Click to expand...

Correct.

thanx guys, srry if i am a n00b.