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So I bought a new Christmas tree this year. One with LEDs which makes setting up and tearing down simple. It has a remote control which can set the lights blinking in different patterns. A lot of really brilliant reds, blues, greens, violet, orange, and white. They can dance and repeat patterns, chase each other up and down the tree, all that. It's really pretty great.

Then I noticed something puzzling. The replacement pack of lights. For the tree they gave me a small packet of 6 replacement LEDs. Enclosed is a picture of one.

My question. How in the world would this work? It's a two wire connection. From the variety of colors there has to be at least 4 LEDs in there - RGB and W. How can the CPU in the base of the tree address any light in the thread and assign it a color with only two wires? Anyone know the protocol this thing is using? How can they get such color diversity and positional addressability from only 2 wires?enter image description here enter image description here

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  • \$\begingroup\$ I doubt the proposed duplicate addresses the question completely, because that question involves self-contained logic. This question involves a user-controllable pattern. Without more specific information about those patterns, how they are controlled, and how the string is wired, I don't know that one would be able to say for sure. But I wouldn't be surprised to find some kind of RF protocol layered on top of the power distribution, sort of like a simple version of powerline network adapters. \$\endgroup\$ Commented Jan 26, 2020 at 0:07
  • \$\begingroup\$ @PeterDuniho together with your comment, it completely answers the question. It's exactly how these "smart" LEDs work: you modulate the supply voltage, and the integrated logic decodes that. \$\endgroup\$ Commented Jan 26, 2020 at 0:46
  • \$\begingroup\$ @Marcus: but the proposed duplicate doesn't discuss any of the "modulate the supply voltage" aspect, and so cannot suffice as the actual duplicate for this answer. If you have specific information about the design and implementation of lights such as the author of this question is asking about, I encourage you to post an answer with those specifics. \$\endgroup\$ Commented Jan 26, 2020 at 5:51

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I think you have to take a closer look at the wiring on those lights. On the picture it is clear that there are at least 3 wires, and the light at the given position only uses one series connection.

So, by changing the used wire at each spot you already have several LED chains. If one of the wires is common then you have two of them, if they circle back to control box then three.

By activating one line at a time you can achieve several moving effects. And if the LEDs change color depending on current direction you can double that amount.

In short - there is no magical "protocol" involved, just clever wiring.

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