Hi there, I'm beginner in arduino and electronics. While I was looking for basic code, I found the blink project http://www.arduino.cc/en/tutorial/blinkwithoutdelay. I searched before connecting where the pin 13 and ground where located and found the same tutorial on the udoo website http://www.udoo.org/ProjectsAndTutorials/getting-started-with-arduino-ide-on-udoo/. I was confused, on arduino website I need a 220 ohm resistor, on the udoo tutorial I could directly connect the led. I tried without and it worked ( ) but I'm wondering the explanation for my future projects... May I follow what I find on websites and arduino's related books or should I always convert/transform sketches and circuits ? My thoughs are : - Udoo doesn't produce the same voltage as a (real) arduino - The LED I use is tolerant and works with or without resistor Thank you for any help / advice
The color of my LED is green, the specs seems to be 2.1V/20mA with this color. I found this wizard http://led.linear1.org/1led.wiz which told me that I need a 68 ohms resistor with the tension of 3.3V. I'm confused as I worked without
You are right, connect a resistor to a LED is always better. To choose your resistor value you need to use Ohm Law: V = I * R V = 3.3 Imax = 13 mA = 0.013 A R = 3.3 / 0.013 = 250 Ohm Basically depends on max current you need on LOAD, led for you.
