LED voltage question and some others.

[Ez Duzit]

So everything I need to start my first mod came in. It's only going to be a nico-stick, but you have to start somewhere right. Anyway I went to rat shack for a couple of pushbutton switches, and LED's. But the led's were all for only 2 volts, except for a few that could handle higher voltage, but they were almost $5 each. Ridicules.
So does the LED rated voltage really matter that much for our purposes. Or is that what the 100 ohm resistor is for? Whats the scoop?

Also, anyone know where I can find a pushbutton switch that doesn't need so much depth to mount it. I'd like to get some really small ones for future builds. Something tried and proven.

Ez

 

[jacko]

The 100 ohm resistor is used to produce about 20ma of current through the LED. At 2 volts, using V=IR, 2volts/100ohms=20ma of current (there is also about 0.7v dropped through the diode[LED], but this is good enough of an estimate).
3.7v/100ohms will give about 30 to 37ma through the LED.... it will make it brighter, but probably wouldn't be enough to burn it out. if you want to be safe, and keep the current down (saving some battery drain), use a higher value resistor with the LED... makes the LED dimmer-not such a bad thing.

 

[Nuck]

To calculate the resistor required for an LED:

LED calculator for single LEDs

 

[rookie20009]

I used these led`s from Radio Shack on my nico stick....$1.49. 2-12 volts and used with no resistor since I wanted the least complicated way I could find. radioshack.com/product/index.jsp?productId=2062567&tab=features

 

[jacko]

It looks like these are 10ma maximum current. You should use some kind of resistor to reduce the current to these.
@3.7v = = 3.7v/.01A = 370 ohms
@5v = = 5.0/0.01 = 500 ohms
And those are maximum currents, so the resistance should be greater than this.