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Sunday, July 31, 2011

Another Battery Powered LED Light Tree

I was in a store in Monterrey CA that sells these really nice 'light trees' last year and I thought that it would be fun to try and make one myself. The first one I made one from scratch, buying all the parts at a hobby store along with LED Christmas Lights, and I wrote about it HERE, (an exciting video of how I made it is HERE). Anyway I was asked to make another LED Light Tree because the first one that I made turned out really nice ;-) When I went to the hobby store again to buy the parts I noticed that they are now selling LED Branch Lights pre-made! This is great because the majority of the effort in making the first LED Branch Light was making the branch itself with all the LED Christmas lights added into it. Check out the above link to see how I did it (or watch the video). I didn't have to do that this time but there were some other interesting things that I discovered while making this one with the pre-made LED branch.
Homemade LED Branch Light Tree
Above is a picture of how this LED Light tree turned out. Looks nice doesn't it? Click on the READ MORE link below to see the parts list and how I built this as well as something interesting I noticed in the battery pack for the LED Branch Light.
The Battery Operated LED Branch Light that I bought is made by Darice and has 20 white LED lights powered by 3 AAA batteries. This was a issue for me because I wanted to put some LED lights in the base as well. The LED lights for the base are the same LED Christmas Tree lights that I used in the first LED Light Tree that I made but they are operated on 4 AAA batteries. The problem is I wanted to power all the LED's off the same battery pack and with the Branch Light using three batteries and the Base Lights using four I had a problem. Before I get into explaining how I got around that have a look at the picture below and the list of parts I used to make this.
Parts For The LED Light Tree
I ended up not using all of the parts in the picture above but most of them. In the blue tote bin you can see the LED Christmas LED Lights that I used in the last tree that I made. There is a bag of colored glass 'stones' made by Panacea "Clear and Blue Mix", the vase that was purchased from Big Lots and of course the Branch Lights on the right.
Back to the different battery pack issue. As I mentioned the LED Christmas Tree lights have a battery pack that uses 4 AAA lights for a total of 6.0 volts. The LED Branch light uses 3 AAA batteries for a total of 4.5 volts. When I opened up the Branch Light battery pack I noticed that there is a 7.5 ohm 5% resistor inside right near the switch. Have a look at the picture below to see what I mean.

LED Branch Light Battery Pack

This is interesting because this appears to be a 1/4 watt resistor and at first glance it looked small to me. So I put the three batteries in the battery pack, turned it on and the resistor got hot! I then put an ammeter into the circuit and I measured 0.195 amps flowing through the resistor. Power = Current squared times Resistance or P=I^2 * R which in this case is (0.195*0.195) = 0.038025 and 0.038025 * 7.5 = 0.285 watts, which is more than the 1/4 watt rating of the resistor. Considering that the resistor is 5% it might get worse. Another thing that I noticed in addition to the LED Branch lights resistor getting how was that the LED lights themselves were brighter than I wanted.
Considering those two things I decided to change the resistor so that the Branch Lights would run off 4 AAA batteries and I could use the Christmas LED Lights battery back to power all the lights. I have a lot of resistors laying around the garage (and house) so I took three 100 ohm 1/4 watt resistors and soldered them in parallel. If your not sure what that means have a look at THIS Wikipedia link about series and parallel electrical connections. The three 100 ohm resistors in parallel make 33.3 ohms and there is about 0.100 amps flowing through them at 6 volts (4 AAA batteries). Because they are all 1/4 watt and in parallel each resistor is dissipating about 0.111 watts - well below the 1/4 watt rating.
The next thing that I had to do was cut the LED Christmas Light strings because there are way too many lights on those strings for the small vase that I have. The LED Light Strings are wired with pairs of 2 LED's in series and all the pairs wired in parallel. Wow that's a lot in one sentence! If you are not sure what I mean and have not read the last post I wrote about LED Light Trees at least have a look at this picture of LED Light Strings wiring that I made. I cut off 3 of each yellow, red and white LED's from the Christmas LED Lights and attached each one in parallel directly to the battery pack. If any of this is confusing leave a comment or send me an email at and I'll be happy to answer and questions that you might have.
At this point all the lights come on and there are three short strings of LED Christmas lights near the base of the LED Branch Light. I put the entire thing into the vase and slowly poured the glass rocks while letting the short strings of colored LED's mix in with the glass rocks. That way the light from the Christmas LED's will mix and blend with the colored glass rocks and make nice colors! That's about it - Yeah!!! This was a pretty fun and easy project to do and I'm sure the person who I give it to will like it.


  1. Wow this christmas tree is looking so beautiful with those LED Lights you have made!

  2. This is really neat! I know my wife will want to make at least one for the holidays, thanks for the "how to" guide and wish us luck as we build our first light tree

  3. Papi Garcia,

    Thanks for checking out my blog, and good luck with the light tree!
    I made a "how to" video as well that you can see here:
    Let me know how your tree turns out ;-)
    - Otto

  4. Brilliant DIY project you have going on here. I gave it a go but I'm pretty much prone to simply laying back and getting some pre-developed LED trees at christmas, it seems too much hassle to set it all up and maintain it considering my family do absolutely nothing to help me.