Hi. I have a question about the lilypad, please! I would like to build something like this
I have those exact items used in that tutorial. (although I'm not sure if my LED is the exact same)
I understand that I can use one LED with that, but what if I would like to connect more than one LED (I'd like to connect two.... or eight. but at least two) The bright white LEDs I have are 3volts.
Do I connect them in parallel? If I get LEDs with even less voltage(is that possible?1.5V?) does that mean I can connect more of them?
With the lilypad arduino and the lilypad power supply(one AAAbattery), what is the maximum number of 3volts normal LEDs I can connect?
I saw a tutorial with the lilypad+AAAbattery powersupply and 16 lilypad-LEDs.
this one: http://web.media.mit.edu/~leah/LilyPad/build/turn_signal_jacket.html
unfortunately I am unable to purchase the lilypad LEDs right now.
Here is the page for the lilypad-LEDs: it doesn't seem to say how many volts it is? I'm probably reading it wrong 
LilyPad LED Bright White - DEV-08735 - SparkFun Electronics
I'm wondering what is the difference between normal LEDs and the Lilypad arduino LEDs? do the lilypad LEDs have resistors/something built in?
thank you so much for reading this, I hope I didn't leave out any information/really, thanks so so much.
there's probably a small resistor on the board with that LED. Do you know what voltage and current your leds want? You can figure out a resistor size from that.
You can run multiple leds using multple lilypad pins. You might also be able to put two leds in series on a single pin - you probably can't run two in parallel. That poor little battery won't last long though with a whole bunch of high power leds sucking at it.
there's probably a small resistor on the board with that LED.
There is it is 100R
You might also be able to put two leds in series on a single pin
Sorry no you can't there is not enough voltage to turn the LEDs on. You require 3V before you start getting any light out of the LED if you had them in series you would have less than 2V across each LED and it wouldn't light.
you probably can't run two in parallel.
If the supply voltage is 5V and it has a 100R resistor and the data sheet says it has a typical 3v3 turn on voltage then you are dropping 5 - 3.3 = 1.7V. So through 100R this gives you 17mA. So two LEDs would give you 34mA which is just about aright (absolute maximum 40mA). However it would be better if you used one LED per pin. You could then power 8 LEDs at only 136mA, the chips absolute maximum total current is 200mA.
Thank you so so much, bill2009 and Grumpy_Mike!!
I see. so it should be okay if I added a 100R resistor to each of the LEDs and connected one LED to one pin? zooms off to try
thank you so much, I appreciate it a whole lot.
if I added a 100R resistor to each of the LEDs
No need to add one. There is already a 100R resistor in that LED assembly that you have from SparkFun. If you were making your own LED module then you would have to add it.
I ran across this message while googling the same issue as the basic math seems to contradict examples of what projects people have created. I found a video demonstrating 20 fading LEDs being attached to the LilyPad unit. I'll post the link below since I can't embed a hyperlink in my first forum post. 
The LEDs in the video are the "LilyPad" style ones that come with the resistor already on board. It appears that the power supply in use is the Lithium Ion battery, run though the LilyPad LiPo PS unit, which supplies the same 5v as the AAA PS, but for a longer period of time.
The LilyPad can also be run off of 3.7V coin batteries, but I'm not sure how much light you'd get out of 20 LEDs, or for how long.
The project I'm working on involves at least 12 LEDs run off the LilyPad, and needs to have the smallest power supply form factor possible. I'll let you know how it turns out when I prototype the circuit and test the longevity.
Here's the link for the 20 LEDs run off one LilyPad: Fading LEDs with Lilypad Arduino on Vimeo