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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:

enter image description here

Notice the little bit of black material inside the LED. Could this possibly be a tiny chip?

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  • \$\begingroup\$ That's a 5mm led, not 3mm ;) \$\endgroup\$ – marcelm Nov 28 '16 at 14:39
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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.

LED Flasher chip inside LED

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  • \$\begingroup\$ Neat, thanks! Unfortunately, mine are diffused so I can't see through to the die. \$\endgroup\$ – Chris Laplante Apr 16 '12 at 22:40
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Yes, there is a chip (probably a simple microcontrolleer) inside the LED.

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  • \$\begingroup\$ Interesting. Does that increase production costs dramatically? \$\endgroup\$ – Chris Laplante Apr 16 '12 at 22:30
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    \$\begingroup\$ @SimpleCoder - Well, what's the difference in purchase price? \$\endgroup\$ – Rocketmagnet Apr 18 '12 at 13:33
  • \$\begingroup\$ Not sure - I scavenged them \$\endgroup\$ – Chris Laplante Apr 18 '12 at 21:54

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