Color-changing RGB Christmas Tree Lights

Here is a quick and easy way to make a strand of RGB LEDs for a Christmas tree.

Step 1 Buy some color changing RGB LEDs

My friend Jimmie turned me on to some excellent color-changing LEDs. There are several kinds of RGB LEDs: the ones with four wires are meant to have their colors mixed by a circuit. The ones with two wires change on their own and can't be programmed. But they are fun and perfect for a project like this. I prefer the ones that change slowly, and Jimmie showed me that you can find these on eBay by searching for rgb slow color change on eBay. They will take a week or more to arrive, which is cutting it close for this Christmas.

Comments

[aaron2william]

This Color-changing christmas tree is fantastic.Christmas is the festival of lights, joys and sweets. Animated outdoor christmas decrotaion looking flashy and eye catching. Baically the lights plays game on the picture and these lights says you that today is christmas.

[jongscx]

Do they randomly change color, or will they all change at the same time?

[bjepson]

They all follow the same cycle, but they get out of sync, so it ends up looking random.

[Edward Nardella]

I would hope there are resistors inside, because the diodes need a current limited circuit. I am wondering if these could be controlled in a fashion via PWM to control the speed of the color change. I would have used the free resistors they include with a 12v Laptop adapter I have laying around. Thankyou very much for posting this project, it is quite cool. Also when you cut the power I wonder if when turned on they start at the same color or reset.

[bjepson]

Thanks, Edward; I'm glad you liked it. I haven't tried PWM with these, but I've wondered if it would be possible for someone to design LEDs like these that give you some control over the pattern or rate: either voltage level or PWM like you suggest. Or perhaps even a third lead that carries a digital signal. They usually do include free resistors with these when you buy them on eBay, but they are for 12v because many people use these in case mods or even in automobiles. And that's a good question about the color: they do reset unfortunately. It's interesting to watch because when you first turn them on, they all start red and then gradually get out of sync.

[Edward Nardella]

Actually the fact that they reset may give more control, I bet the circuit has to be off for a certain amount of time (IE 10-20ms) before it will reset. So if you do not turn it off for more than that cutoff you may be able to do some neat things.

[inventorjack]

That's crazy! I was thinking about something like this earlier today at work. Then I come home, go on make, and see the link here to your instructable. Awesome! Thanks for sharing.

[richms]

I would twist the wires before soldering since I can see that it would be a huge tangling hazard with them separate. I used some of those leds a while ago for another project and had quite a high failure rate where one of the colours would not work, hopefully china have improved their QC in the couple of years since then.

[Edward Nardella]

The circuit does not need resistors for each LED?

[bjepson]

Hi Edward,

These do not require resistors at the voltage I'm using. These LEDs are a bit unusual in that they have a small chip inside of them that is powered by the battery. The chip then powers each individual LED element as it cycles through the color sequence.

I've seen spec sheets for this kind of LED that say 3.8-4.5 V for Vf, and even though I'm underpowering them slightly with the rechargeables (3 x 1.2v), they are plenty bright.

There are a couple US suppliers for these LEDs who have posted spec sheets, but they are much more expensive than eBay. However, if you want to get the LEDs quickly, they may be the best bet:

http://www.elexp.com/opt_hrgb.htm
http://superbrightleds.com/specs/rgb-acc-spec.htm

- Brian

[bjepson]

Also, I think there may be resistors inside the LED, because each element has a different Vf.