Hello
It's a basic knowledge, but I'm confused and post a question.
I'm going to connect 10 LEDs in a bundle and connect them to one data pin of Arduino. In this case, is the resistance value is (resistance of LED * number of LED)?
For example, if the voltage of the Arduino is 5v, the voltage of the LED is 2v, and the current is 20ma, the resistance is 150 ohms. Then is it 1.5㏀ if I use 10 leds?
Thank you.
How much current in total will the 10 LEDs take ?
Parallel or series?
So 10 leds in parallel is 200mA, and that's way beyond what you can draw from a microprocessor pin.
So let's start over. You need more light than you get from a single LED. What's the application? Shall we try and look for a solution that may actually work, yes? 
10 leds in parallel, each with a 1k5 resistor will be (more or less) the same as 1 led with 150 Ohm resistor.
Yeah, but notice that OP seems to want to treat the LED as a resistor, which is what (s)he was talking about in the context of the 150R/1k5. This was not about the current limiting resistor.
you gonna have 3mA drawn from MCU pin then shared between 10 LEDs, don’t think it will be enough to light up any
@yscheol, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for 'problems' with your project See About the Installation & Troubleshooting category.
All sorts of possibilities, sterretje has the correct arrangement, lets see if that was what the OP was meaning? 