# LED Christmas Tree

A nifty little LED Christmas tree made from nothing but LEDs, resistors, and a found power supply.
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## Step 1: Parts

This tree has made of 17 Red, Green and Yellow LEDs - the cheapest the electronics store had in stock. (no idea what manufacturer)
Their specs: (same for all colours)
forward voltage drop = 2.0V
max continuous current = 15mA
If you can, try to get LEDs that have the same specs - it's easier to design your tree.

The power supply used is from an old printer found out on the street - any sort of DC power supply will do, but the higher the voltage, the better. The one I am using supplies 30V, at up to 400mA. Enough power for 300 LEDs, but that's overkill. :-D
ashcooper4 years ago
Nice instructable.

i am very new to Instructables and my electronics knowledge is very basic.  I need to make a circuit of 150 LEDS.  But the distance between each LED will vary with the smallest distance being around 5cm and the greatest distance being about one metre.  When you say:

Try not to make the distance between connected LEDs any more than twice the distance of the LED's leads, or you'll need to use extra wire (complicated)

Is there somewhere you can point me online where I can see what you mean?  How complicated is it and will it make it extremely difficult if the distances between the LEDS varies?

I want to use a 12v power supply, not a batteries.  Maybe LEDS are not the way to go with this project?
MrTrick (author)  ashcooper4 years ago
Thank you!

With a 12V power supply you can run as many LEDs as you want, but not necessarily all in series. The way to do it is to experiment with your LEDs and a resistor to see how many LEDs can be run in series, like:
12V ------[LED]--[LED]-......--[LED]----[resistor]------0V
And then build as many parallel chains of this configuration as you need for the project.

The size of the resistor will affect how bright the LEDs are.
The brightness of the LEDs will affect how much current each chain will use. (If very bright, up to 20mA)
The limit on how many LEDs you can drive will be the current rating of the power supply. If it's rated at 500mA and your chains each use 20mA, you can have up to 25 chains.

Hope that helps.  :-)
4 years ago

OK, so I can have a single 12V power supply with multiple chains in parallel circuits running from it.  I just need to do the math or...

I will use http://ledcalculator.net/ to design the circuit and ensure that I have the specs of the LEDs correct to limit problems with blowing the LEDs or them getting too hot etc.

My question is whether or not there is any loss in power if I am wiring the LEDS one metre apart?  Will I have to take into account current (?) loss over the length of the wires? Or is the loss minimal?

As I am trying to wire a lot of these things over a 5 x 5m wall at varying distances I am assuming that the length of the wires will come into play when doing the math for the circuit(s) design.  But maybe I am wrong?

Sorry for my ignorance and thanks for your help.

MrTrick (author)  ashcooper4 years ago
There is no problem having longer wires. The only reason I stipulated putting the LEDs close together for this instructable was that they're soldered directly from one to the next. If they were further apart you have more joints to solder.

So for the maths, don't worry about the wire length.

Good luck with your project! :-)
imarzouka6 years ago
You can also use this calculator

http://ledcalculator.net
MrTrick (author)  imarzouka6 years ago
Hey, that is a great tool! For those who aren't confident with electronics, at any rate.
T3h_Muffinator7 years ago
Nice! Reminds me of my first instructable!
MrTrick (author)  T3h_Muffinator7 years ago
Yours is wired in parallel, no? Any problems with slightly different voltage drops among different LEDs? (cause you don't have a resistor for every LED) I like the 3d-ness of it... perhaps next year I'll take the power supply off this and build a bigger one, with lots of 2D 'slices' that make a nice big tree. 30V/200mA should get me a lot of serial/parallel chains.
7 years ago
Yep, mine's all in parallel. I actually do have a resistor for ever LED; they're in parallel, and I have 3 strings of LEDs, so there's 3 resistors (which are all made up of two resistors each). I take care of the slightly different voltage drops w/ different resistor values, and each string is only for one color (green & blue values are so close I counted them as one). Definitely make a 3-D version! it's awesome!
zjharva7 years ago
i had been thinking about making something like this for a while. Nice instructable!!
Kiteman7 years ago
Very nice, and versatile, too - it could be re-shaped to match almost any festival for any religion that celebrates light (Diwali, Hanukkah, etc)

## +

GorillazMiko7 years ago
another instructabler posted something like this, but his was WAY too hard! great instructable! (favorited)
MrTrick (author)  GorillazMiko7 years ago
Thank you!