Short version :
How can I control 20 leds in a binary clock without them blinking or dimming with enough space to add buttons and speakers etc with Arduino Duemilanove ?
Long story:
So, I'm building a binary clock, built the first version using this schematic - Project Potpourri: Your Favorite Geek Desk Toy Sucks , except I have tens of seconds/minutes/hours too.
It works well, but as I am currently addressing the leds in X/Y coordinates, blinking them one at a time, the more leds there are, the shorter the blink and dimmer the led.
To reduce the dimming and blinking, controlling each led individually would be best, but as would like to add buttons to change the time, and maybe make it an alarm clock, I can't use all the I/O pins for the leds.
I thought I could separate the minutes, hours and seconds so change in seconds wouldn't dim the others, but that would still use way too many pins.
I guess I need some additional chips, but I have no idea what would work.