Hi all, I just got my Arduino a week ago... so much fun! I've been reading the forums and feel like after all of my research on here it's time to check my ideas!
The Concept: I'm working up to make a 72 led array in 6 sets of 12 yellow LEDs They are programmed to turn on and off the 6 sets throughout a 6 month period.
Program: Adjust http://arduinoarts.com/2011/08/arduino-tutorial-the-knight-rider program to have longer delays and use only 4 pins. ie. adjust "int timer = (*) ;" * to the equivalent of a full day Then add another "blink" code with a long delay on the 2 remaining sets of 12 LEDs for 2 more pins for a faster sequence running at the same time.
Hardware: Arduino LEDs Wires Resistors Transistors Breadbord
Hardware Layout: Pins 3-8 each run through->appropriate resistor-> base pin of appropriate transistor then run 12v external power->appropriate resistor->12 LED array-> current pin on transistor-> exit pin on transistor to ground.
Questions: Can I run the whole lineup through a single transistor or do I need one for each output pin? What would said transistor(s) appropriate value be? How do I figure out the appropriate resistance values for the pin-> Transistor resistor values? and the Power-> LED resistor values If some of my LEDs are mismatched do I run them in series or parallel? (some dimming is not a big deal, they are mostly hidden/subtle lights anyway)
Thank you everyone who replys on these boards! I have already learned so much! and am excited to learn even more! -Andrew