The Cylon eye / Knight rider effect.

Using the same circuit arrangement as previously posted, we can turn our simple light meter into a Cylon eye! This shows the flexibility of the Arduino and how powerful software can be:

int counter = 0;
int direction = true;


void setup() {
 PORTD = B00000000;
 pinMode(0,OUTPUT);
 pinMode(1,OUTPUT);
}

void loop() {
 if(direction) {
   counter++;
   if(counter == 7) {
     direction = false;
   }
 }
 else {
   counter--;
   if(counter == 0) {
     direction = true;
   }
 }
 PORTD = 1 << counter;
 PORTD = PORTD | 1 << counter + 1;
 delay(80);
}

The effect could probably enhanced by adding capacitors between the base and ground on each transistor, causing the adjacent LEDs to fade in/out.