smh_999:
Hmmm...Having read last two posts, I'm now thinking shifter registers x 2Found a great tutorial: http://bildr.org/2011/02/74hc595/
Impressed...I now know what a shift register does! 8)
I'm getting the SparkFun Inventors kit, which happens to come with a 74HC595, so I can at least get something running as a prototype (of a prototype!) before commencing the build.
Thanks again all...Excited and looking forward to getting started on this!
By all means experiment with using shift registers to educate yourself. However, I think using 74HC595 shift registers for this application is a silly idea. You will need three 74HC595s (assuming you drive the 25th LED direct from the Arduino, since three 8-bit shift registers gives you only 24 outputs), and they have a lower output current rating (25mA per output, 50mA for the whole package) than the Arduino pins (40mA per output, 200mA for the whole package). You will also need 25 series resistors instead of 5. The only advantage of using shift registers is that you can drive 24 LEDs (or more, if you use more then three shift registers) from 3 pins. But it does not sound to me that you are short of pins, so I suspect you can easily spare the 10 pins that a 5x5 matrix needs. Why use more components and wiring that necessary?