Hi guys,
This really would be a 'cute' project for a little 8-pin PIC ($1.60 USD)... The LEDs are multiplexed using the N(N-1) scheme and could be scanned one column at a time (from schematic point of view) for decent brightness at a 20% duty cycle and a >100-Hz refresh rate using a Timer 2 interrupt routine... Use high efficiency low current LEDs (5-ma) and you could probably run the thing off a couple AA batteries for a good length of time and the hardware couldn't get much simpler; an 8-pin PIC, 6 resistors, a 0.1-uf bypass cap', and up to 20 low current LEDs... Pretty cool -- yes, no, huh?
Regards, Mike