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How many LED's can you control?

Hi All!

I've got in mind a project that will involve a couple hundred LEDs that have to be independently controlled. I want to  make a clock where the individual seconds, minutes, hours, days of the month, and months of the year are represented by a lit LED. As the LED's representing seconds passes 60 seconds and goes to the next minute, all the "second" LED's go out, one "minute" LED turns on, and the seconds start over with all of them being dark. The process repeats indefinitely and cascades into hours, days, months. 

So to my beginner's mind, I'm thinking I need one output pin per led. If that's so, how would I go about controlling a couple hundred? Can you chain processors together? 

Thanks!

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a better option would be to use registers such as the 74374.  With these you can easily achive a large amount of individually adressable outputs from a small amount of outputs.  If you use a decoder on the address lines it will decrease the required microcontroller pins even more.

SIPO shift registers are another option, but are somewhat more complicated to use and far slower.

 

You can use an LED matrix driver, and use a serial port of your processor to send commands. Do some searching on this site and elsewhere and you should find some appropriate stuff. Here's one:

http://letsmakerobots.com/node/21786