I have a few 3mm color-changing LEDs which I harvested from a toy. They fade in between all different colors, and then after a little while, they blink crazily between all the colors. After a few moments, the cycle repeats.
What is interesting about them (and what I wasn't expecting) is that they only have two leads, like a normal hobbyist LED.
I understand that, like an RGB LED, they have multiple elements (probably not the right word) inside. But how do they achieve the color changing and cycling?
Here is a picture of the LED in question:
Notice the little bit of black material inside the LED. Could this possibly be a tiny chip?
Answer
I expect they contain a tiny chip (you can see the little black thing inside) which sequences the patterns. It's either a microcontroller or a special purpose IC.
Most likely something like one of these:
They're available in bare die form and connected to the LEDs inside by ultrasonically welded little wires.
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