I tried to do the right thing by moving this post over to the E-textiles forum, but apparently I cannot delete my own posts 
Sorry for the double post LilyPad how many LEDs per petal? - E-Textiles and Craft - Arduino Forum
Hi all, newbie here trying to figure out how many LEDs I can run off a lilyPad petal for a small project.
If one LilyPad Micro LED takes 20mA of current, but one petal outputs 40mA, then how does Leah Buechley manage to string 7 LEDs onto one petal in her tutorial?
According to her design, you can string 7 LEDs onto one petal: http://www.flickr.com/photos/leahbuechley/2596552004
But according to the specs on of the LilyPad Main Board the DC current per I/O Pin is only 40 mA
http://arduino.cc/en/Main/arduinoBoardLilyPad
Asuming that each LED will consume around 20mA of current, how is it possible to string 7 of them together onto one petal?
Unless each LED is eating way less than the 20mA's?
Also, not sure how I would use Ohm's Law to calculate anything here. I know the current (I) as 40mA, and I know the resistance of the thread as 28 ohms per foot (lets say 2 feet are used, so 56 ohms). So I can use Ohm's Law to calc the volatge needed as 2.24 volts. But not sure how that helps me? I plan on using a 3V 250mAh coincell battery to power the lilyPad itself.