How many LEDs can the Arduino run?

Hi,

I was wondering how many Tri-color RGB LEDs I can connect to one Arduino Duemilanove. I'm planning to use PWM output to change the color of the LEDs. I'd like all the LEDs to change color all at once.

Thanks!

Each pin can provide 40mA of current but the total current through all the pins is 200mA. If you need more current than that you will need to use some kind of buffer. Have a look at the Arduino playground for some ideas on how to do that.

And of course, the Arduino as many microcontrollers; only has a very limited number of PWM outputs. If you were thinking of making some kind of display of any sort you would probably want more than that!

For this application I would recommend using a display driver. Like these Maxim ICs: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4539