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This is a pretty simple project that makes a cool, flickering led star! Perfect for the holidays!

Time needed: A few hours

Complexity: Low

Cost: For materials, <$5, for arduino board: around $30

Skills needed: Soldering

Step 1: Materials!

This is a very simple project and only requires a few parts.

1x Arduino. Anything from an ATTiny to an UNO will work, as long as you have the means to program it. This will not work with a Mega. Sorry!

LED's, any color (preferably yellow/orange ish. Any color will do though). You will need 30-50, depending on how big/what shape you want your star. The LED's I got were clipped short, so it was harder to solder.

Perfboard. I used an 70x90mm sheet. 

Wire

Soldering tools (soldering iron, wire strippers, helping hands etc)


Step 2: Arrange LED's

I decided to arrange my LEDs in a classic, 4 pointed star shape (Star of Bethlehem).
It is the basic shape of this:
4point star

You can do any shape you want here, just remember, the more complex it it, the harder it will be to solder.  Also, make sure to arrange your leds in a way that will make sense. Make SURE your LEDs are arranged in the correct polarity throughout the project! Otherwise, it will be very confusing and you may have LED's that wont work! 

Step 3: Tape Down LED's

Once you have arranged your LED's the way you want, use tape to secure them to the perfboard. You have to do this unless you want to solder the LEDs in one by one. 

Step 4: Mark Your Paths

This is something I neglected to do with my board. I highly recommend you try it. Just use a sharpie or something to mark the side if the LEDs that will be hooked together, and do it for the other side with a different color. Because I didn't do this, my leds were soldered down wrong, and I had to re-do a lot of the board. Attached is a crudely drawn image of what my LEDs might have been marked like:

Step 5: SOLDER!

Bend the legs of the LEDs so that they all connect together in parallel. Solder everything together.This step takes the longest time. Test every few minutes to make sure you don't have any shorts. Double check the leds before you solder. You might need to have some wire jumpers near the points of the project. I had to do this. 
Solder 2 wires onto the + and - leads of the led's. These will go to the Arduino

Step 6: Get the Arduino Library.

For this project, I used the TrueRandom library: you can download it here
T
here are also instructions here for how to put the library in the Arduino Software

Step 7: Code the Ardunio

Open the Arduino software and start a new Skech. Insert this code 
#include *TrueRandom.h* void setup(){ } void loop(){ analogWrite(9, TrueRandom.random(0,255)); delay(10); }
Replace the *'s with < and >,  and upload it to the arduino. Plug the positive wire of the star into pin 9 of the arduino, and the negative wire to ground. The display should light up and "flicker". That's it! All done. In my project, note that I have not used the center LEDs yet. I am using them for something else :)



Thanks user oweng4000 for the code! Also, many thanks to user Robot Lover, for putting on the advent calendar, and doing such a great job on it.  How about a quart of oil for the Robot, huh? Cheers!
I figured a transistor would be my best option. I have a 5V 1A power supply and 103 LEDs. I made a snowflake with amber LEDs.
Yep- you should be alright as long as you use a transistor rated for over 1 amp of current (just to be safe). You could also use maybe 5 or so 2N3904 transistors in parallel- but it is probably better just to get one transistor. Also make sure your LEDs are using around or less than 10ma of current each or you might overload your power supply. You could probably use a few resistors to keep the current for each LED under a certain amount
Is there a limit to how many LEDs you can use?
I would try to limit it to less than 20 at any time using an arduino pin for power, but if you use a transistor to hook it to a wall wart or any power supply that can support more amperage, you can use quite a few LEDs. I'd say a 5v 1A power source could do about 100 LEDs at 10ma each. More if you used lower power LEDs or got a higher amp power supply. What are you trying to do? :D
I know what its like to have a crappy soldering iron I own one.
Excellent job!!
This is great! I would make this but sadly, I don't have any orange/yellow LEDs. Maybe I will make a twinkling tree ornament. Love it!
Thanks. I almost put this on top of our tree, but I'm not sure what mom would say :)
Hah! We actually couldn't find our tree topper so I was just about to make one until my mom bought one :(
aww. You should &quot;lose&quot; the new one.. if you catch my drift ;)
Ha! I think she likes it too much!
shoot. Well, there goes that idea!
Very nice astroboy907! It looks really good in action on your video. <br><br>I'm new at Instructables, so I'm not sure if this is correct, but my understanding is that you must post your video to a site like YouTube or Vimeo and create a link to it. Currently your video is playing automatically, even if you're not at that step, and because there are no video controls, you can't pause it or anything.<br><br>So, I might be wrong, but you should either post the video elsewhere, or confirm this fact with a member who's been around longer than I have.<br><br>Regardless, I think it looks great. Thanks for sharing!
Ah. I embedded it rather than opting for the youtube method. I shall turn autoplay off...
Fixed! Ended up uploading to youtube..
Much better. It looks great!

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