Eyes are tricked very easily. With 3 groups of LED's you see the movement, and you can even play with different duty ratios:
Having either lights or "black holes" moving around
(For symmetry you'd need 12 or 15 leds, though)
Thanks for the insight, Michael. Is there anyway you could expand upon this or lead somewhere that might explain it in detail? I'm a little confused about how to get the chasing light effect without each being seperately controlled, but I'm very curious to hear your idea.
Just tie the series pairs to pins 2..8 and see if the brightness is sufficient.
Fairly sure you are, but are you saying have 2 LEDs in series connected to pin 2, then 2 LEDs in series connected to pin 3, and so on until 8? So, if I have 7 sets of 2 LEDs in series, would that mean I only need to provide half of the mA? 7*20mA = 140mA + 40mA [for the Arduino] = 180mA... does this sound correct?
(To be on the safe side, test a single LED in series with a 120 Ohms resistor and verify the voltage drop is about 2.5 / 2.5 and the current is ok)
Are you saying to hook the LED through a resistor and into the Arduino with power (5V) and then test the voltage drop? What current would be okay?
So 9V on Vin will still result in the I/O pins being (about) 5V, because there is an on-board regulator that regulates the 9V down to 5V.
Thanks for clarifying, James! So no matter what the power source I'm putting into the Arduino (volts-wise) I can plan to use a resistor that would be sufficient for 5V, correct?
Appreciate all responses, guys. Getting more and more comfortable with all this.