Noob Led question...

[night-B]

I just ordered a hundred ultrabright Led from china. I don't know wich resistor value should I choose. I know it's calculated by U=R*I. U is a 9v battery but what is the intensity in a 9v stombox circuit, applied to the led? I found that these leds must run under 3.2V and 20mA.
I wanna build a light emitting border of plexi like this one
http://www.diystompboxes.com/smfforum/index.php?topic=66840.0
If I put two leds in series, should I change the resistor?
Thanks guys

Jul

[stecykmi]

LED's are pretty forgiving. The "standard" value is usually given as 4.7K ohms, but you can go up to, say, 1k, and that's really bright. It depends how bright you want it. If you're doing two in series, choose a value that's somewhat lower than 4.7K. Maybe try 2.2K or so.

[night-B]

Thank you!

[madbean]

For ultra bright, I use a 10k.