I'm a beginner in electronics and Arduino and was hoping to get some clarification on how the output pins on my Arduino Uno work with multiple LEDs.
I had an idea for a project that would consist of a bunch of LEDs (somewhere between 30 to 50 I guess) arranged in a circle and connected to an Arduino that could be worn like a necklace (the Arduino would be used to create a light show of sorts). To simplify the project I was planning on connecting 3-5 LEDs each to 10 of the digital output ports (for a total of 30-50 LEDs, driven in groups of 3-5) instead of trying to use an LED driver (I think that's what the IC is called), but after some research and experimentation I don't think it is realistic to connect and use that many LEDs at once.
I have a ton of questions about electronics and Arduino; it would help me a ton if you could answer any of my questions, which may be horribly misguided to begin with. Also, please explain anything like I'm five years old as I am very confused as it is.
1) Is there a limit to how many LEDs that can be connected to the Arduino? I know this answer will be different for each type of LED, but let's take one of these http://www.sparkfun.com/products/9590
as an example.
2) I read that each output port has a current of 40mA, but with a resistor added I would think the current would be decreased (I=V/R). Is 40mA the limit then, or is there a limit?
3) Does the resistance of a resistor connected in a series with and LED affect the voltage drop of an LED? One website I visited said that the voltage drop is always the same for an LED, but in my physics class (I'm a high school student btw) we learned that the voltage drop across a resistor (R1) connected in a series with another resistor (R2) is related to the resistance of the second resistor (R2). So, assuming the voltage drop of an LED is constant, does this mean that if the voltage drop of an LED is 1V, only 5 can be connected to an Arduino (correct me if the voltage difference is not 5V, I thought it was for some reason)?
Thank you for your help!