Auto Cycling LEDs

A product that many people may not be aware of is auto cycling LEDs. These LEDs have a build in IC that will cycle the LED between multiple colors. Digi-Key has a selection of RGB LEDs that will cycle without a microcontroller. Another feather of these LEDs is that they will accept a range of voltage and the IC eliminates the need for a current limiting resistor.

Sparkfun offers this diagram in their data sheet.
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While you can see a slight internal change over a standard LED it is hard to tell the difference without looking closely.
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Another neat group of LED to look at for your next project is Flashing LEDs that will automatically flash / blink without a micro.