Introduction: Arduino Powered Musical Christmas Lights

After exploring the Instructables website I found a few projects that peaked my interest and those lead me to thinking, I could make some musical Christmas lights. Most of what I spent my time on came from Amanda Ghassaei's Instructable on Frequency Detection. I owe a lot to her work! The rest is simple use of relays.

I also want to preface this Instructable with the fact that I did not make this one to look pretty behind the scenes and some of the pictures will not match my instructions because after doing the project myself there are a few things that I would do differently, which I include in the Instructable. Also, I am by no means a professional! This is a recent hobby and I am sure that many improvements could be made, so feel free to make improvements but please leave comments so that people can use them in the future as well.

Items you will need:
Mp3 player (any will work)
Stereo with audio in (or transmitter if you already have the know how to broadcast like the cool houses)
3.5 mm audio cable (from old head phones or wherever)
3.5 mm audio splitter (one lead to the Arduino the other to the stereo)
Arduino Uno
2.1mm power plug (for the Arduino)
Extension Cord (that you can cut up and use)
2 10k resistors (brown, black, orange)
1 10 µf capacitor (polarized)
5 150 ohm resistors (brown, green, brown)
1 pack of jumpers and headers  (
5 Solid State Relays  (digikey part number 425-2395-5-ND)
Protoboard (preferably one with the copper rings)
Solder-less board (optional but encouraged)
5 electrical Sockets from local hardware store
Electrical boxes for the sockets
4 Zip ties and a drill

Step 1: Setup Audio Input

The first thing that you will want to do is setup the audio input and test it to make sure that you are reading frequencies. To do this you will want to set it up the components like in the schematic shown on this page. I recommend doing it on a breadboard first so you can test it before soldering and committing to the setup.
Attached to this step is a compressed file with an Arduino Sketch you can load directly to your Arduino. Once you load the program and start playing a song you can look at the frequencies using Arduino's serial monitor or make a txt file using the program I built, which is also in the file.
Once you are sure that the configuration is working for you, solder a pair of the jumpers from the jumper kit to the bottom of a protoboard to plug into your Arduino and solder your other components together on the top with the resistors soldered to the jumpers.

Your Arduino will power itself through the USB cable, but if you are like me you don't want your computer attached to this all of the time. So this is where your power connector comes into play. The Arduino uses a center positive configuration and can use 7-12 volts ideally (see for details). Find what wire goes to the center and hook that to the positive of your power source and the outside sleeve to the GND or negative. You can use a 9V battery or any other power supply that meets the Arduino's requirements. I personally tried a 9V battery and changed to one of the 12V leads from the PC power supply that I use to power my car stereo deck converted to home stereo that I use with this project. Just a warning, if your battery voltage drops below about 7V the 5V output drops to about 2.49 and your display stops working. I had this happen once, right after making a few changes to my setup, and it took a few minutes to figure out for sure that the battery was too low and causing the problem.

Step 2: Test the Digital Outputs

Now you will want to speed up your program. To do this comment out the lines:

Serial.println(" hz");

Once you have commented out these lines and uploaded it into the Arduino you can test your output one of two different ways. You can either skip this step and just hook up your relays and test with the relays, or you can use LEDs. I personally tested it with LEDs first because they have the same power requirements, depending on your LED, as the solid state relay. 

To test with LEDs just use a jumper to bring the ground from the Arduino to the ground rail on the breadboard. Plug each LED's cathode into the ground rail and then use the 150 ohm resistors to connect pins 8-12 to the anodes of the LEDs. Enjoy the light show!

Step 3: Wiring the Outlets

After testing to make sure this all works you will want to assemble the outlets and test the relays themselves.  I apologize for not having more pictures but I made the lights and then decided to do the Instructable and I don't want to take it apart just for pictures. So please make sure that you read all the way through first, then do. 

The first thing that you will want to do is connect your electrical boxes that you got for outlets. To do this you will be making two pairs of holes, one set towards the top of the outlets and the other towards the bottom, about halfway from back to front. These wholes will be for the zip ties to go through. Start by grabbing a box, I recommend a bigger one first, and drill the first pair of holes about an inch apart and then drill the second set about the same. You will have to do this again in the other boxes to link them together so I recommend using a marker, or something you can see on the boxes, to mark through the holes you just made and onto another box. This is why I recommend starting with a larger box. Once you have drilled the holes, lace the zip ties through and tighten them to link the boxes. If you like you can use other creative methods. 

After you have the boxes together then start wiring. Here is where you will want your extension cord. I used a stiffer wire, generally used in walls, and it was much more difficult to work with and made soldering problematic. Inside your cord there should be three wires black, white, and green.The black is the "neutral" wire, white the "hot" wire, and the green is the true ground wire which is connected to that bottom third prong. Connect the neutral wire (black) and the ground directly to your outlet. if you don't know how to do this ask someone at the hardware store or a friend who knows more, otherwise just don't do this project because this is high voltage and can hurt you or others. Since the neutral and ground are directly connected you can link all the plugs together with the neutral and the ground. It is the hot wire that we will be using with the relays. DO NOT string the hot wire (white) together between outlets or your lights will always stay on. Use the hot wire from the cord, left over from connecting the outlets neutral and ground together, to make a separate lead for each outlet which will connect to the relays.

Now the relays. On each relay there is 4 pins two marked "~", one "+" and one "-". Place each relay on the protoboard with 3 rows between them so that they won't touch each other when soldered together. Solder all of the "-" together with a wire, or jumper, for easy connection to the Arduino's GND on the digital side. Now solder each of the 150 ohm resistors to their respective relays. Use a row of 5 jumpers to easily and cleanly connect the jumper wires to the Arduino, then connect the other end of the jumper wires to the resistors that you just soldered to the relays "+" terminals.

Now solder all of the inside "~" terminals together and solder the hot wire from your extension cord to the row as well. Now Solder the individual wires from your outlets that you connected earlier to their respective relays outside "~" terminals.

Once you have soldered all of these together make sure that your outlets are covered and plug in a string of lights to each outlet set and test your configuration just like in step 2.

Step 4: Enjoy!

Now that you have everything hooked up and ready to go, feel free to tinker with the code but make sure to put comments on the page if you find anything better so that others can enjoy the improvements as well.

I will try and do my best to answer any questions and others feel free to answer questions if you know the answer. 

Youtube video:

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