Running Multiple Segmented LEDs

I was just wondering, if it takes 7 digital IO pins to run 1 7-segment LED, how would one utilize 3 7-segment LEDs on the arduino (say for an alarm clock?)



You would probably have to multiplex the output somehow. There are multiple techniques. A quick google search for an LED display driver gave me this appnote from Maxim:

The maxim chip MAX7219 i think was originally designed for 7 segment LEDs. The data sheet has I think all the required info, if you are lucky you will be able to use the examples for this chip included with the arduino environment.