Color-changing RGB Christmas Tree Lights




About: I'm a Content Manager for LinkedIn Learning. I like to hack code and things.

Intro: 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.

Step 2: Tools and Supplies

You'll need:
  • A spool of green wire wrap (30 AWG) wire
  • Wire wrap tool with stripper (or any wire strippers that can handle this wire)
  • Wire cutters/snips
  • Soldering iron
  • Glue gun
  • Panavise Jr. or helping hands
  • Solder
  • LEDs
  • 2 or 3 AA battery holder

Step 3: Prepare the Wire

Now you need to cut two wires to the lengths you want. One will be the positive side, the other will be the negative side. Strip one end of each wire and (optional, but recommended), tin the ends. Next, connect one wire to the positive lead of the battery holder and the other to the negative. Insert the batteries (3 rechargeable AAs worked best for me, 2 alkalines would probably work fine).

Now you have a live wire, so avoid shorting it out. Keeping it live while you assemble the strand solves two problems: you'll know immediately if you have the polarity reversed, and you'll also know immediately if you've damaged an LED.

Step 4: Create Contact Points Along the Wire

The next step is to use the wire stripper to create contact points along the way. You can do this by sliding the wire stripper into the wire and exposing a small amount (2mm or so) of wire. This makes the project go a lot quicker than if you were cutting lengths of wire between each LED.

Open a contact point on both the positive and negative strands at the same length along the strand. Remember that the power is still connected, so don't short the wires.

Step 5: Tuck the Exposed Wire Under the LED's Leads

Next, bend the leads of the LED as shown and tuck the bits of wire you exposed: positive to the long lead, negative to the short one. The LED will probably flicker on and off because the connection is not secured yet. Now you're ready to solder the LED in.

Step 6: Solder It

Put the LED into your helping hands or Panavise, and solder the lead to the exposed wire. See if you can keep it close to the start of the lead. Avoid shorting it out here (it's easy to accidentally touch the soldering iron tip across both leads) because it could damage the battery. Be especially careful with rechargeables. They should never be shorted out.

When you've completed the solder joint, clip the leads as close as you dare to the joints. Insulate the solder joints with some hot glue, move on to the next point along the strand and return to Step 4.

Step 7: Finish It

Keep going until you're happy. The more LEDs you use, the faster you'll wear out your batteries. I get 3-4 hours from 3 AA rechargeable batteries on a 45-LED strand. You can, of course, use some kind of wall wart, but don't give these LEDs too much juice or they will burn out.



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    11 Discussions


    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.


    Reply 9 years ago on Introduction

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

    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.

    2 replies

    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.


    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.


    9 years ago on Introduction

    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.


    9 years ago on Introduction

    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.


    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:

    - Brian


    Reply 9 years ago on Introduction

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