Mubanga:
Thanks John! Although this way I won't be able to use shift registers won't I? because in my final project I will be using 27 LED's. But that's not to big of a problem, in that case I will use I2C I/O expanders.
You can use an unsigned long (32-bit integer) to keep track of which LEDs you want on and off.
int timer = 1000; //Sets timer
const int pinCount = 6; //Sets the number of pins
int Number = 3; //Sets the amount of LEDs that will go on
unsigned long pattern;
int thisPin;
int alreadySet;
void loop(){
// Turn off all the LEDs
pattern = 0;
// Turn on "Number" randonm LEDs
for (int i=0; i<Number; i++) {
do {
thisPin = random(pinCount);
alreadySet = pattern & (1<<thisPin));
pattern |= (1<<thisPin);
}
while (alreadySet); // If the LED was already on, try a different one
}
// Send 'pattern' to shift registers
delay(timer);
}
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