Christmas light bulbs are incandescent and burn out at an ever increasing rate. This was fast enough that my roommates and I got blisters from pulling them. I had those lights up for over two years and I wasn't about to go without ambient lighting. I figured LEDs were the way to go.
Each module is powered by 12V and is relatively simple in concept. The number of LEDs you need per module depends on the voltage of the LED. You'll typically be able to get 3 blues or greens (3.4V each) on a module or 5 reds (2.4V each) on a module. A VERY large number of modules can be powered off of one supply. The maximum number of modules that can be powered by a single supply can handle is its amperage divided by the current a single LED pulls. In my case, I used a 12V 5A power supply from Digium and 20mA LEDs, so that gave me 250 (5/0.02) modules per supply. That's a whole lot of light!
Parts for each module:
A piece of breadboard
3 blue LEDs (3.4V)
A 100 ohm resistor
2 small neodymium magnets
2 ferromagnetic thumbtacks
Hot Glue Gun
A 12V Power Supply
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Step 1: Materials and Organization
Your first task is to gather your materials and find the module configuration that suits you. For each module, you'll need some perfboard (the really cheap stuff if possible), a 100 ohm resistor, three 3.4V blue LEDs, two 1/8"x1/8" neodymium magnets, and two ferromagnetic thumbtacks. For general supplies, you're going to need a 12V power supply, some cheap speaker wire, a soldering iron, some solder (lead/tin), a hot glue gun, and some glue sticks to go with it. A third hand pcb holder is helpful, but not required. As for organization on the perfboard, it's really up to you, but I chose long and skinny so my modules would have a similar profile to the wire itself and be less obtrusive.
Once you have decided where the LEDs go, make sure that they are in the correct orientation. The longer lead is positive and goes away from the resistor. The resistor will be the link to the ground for the module. I left a gap between the perfboard and the LEDs so that I could bend them and better distribute the light. Bend the leads that are going to connect toward each other so that they lay parallel and almost touch. The end result of this is shown in the next step.
Step 2: Soldering and Coils
Now that you have your LED and resistor leads bent to the proper positions, you'll need to solder them together and clip off the excess part of each lead. Take care NOT to cut the outer leads as you'll need them in a minute. Try to use the minimum amount of solder that is necessary.
Take one of the magnets and bend an outer lead around it, creating a spring or coil-like structure. This will help hold the magnet in place and maintain conductivity. Once you have both ends coiled properly, insert the magnets and make sure they still fit. It is fairly easy to mess this up, so you may have to practice it a little.
You must be VERY careful on this step or you will ruin the magnet. Even relatively short term exposure to high temperatures can cause the magnet to lose its magnetism. Since the resistor lead isn't magnetic, I would suggest using a tiny bit of solder to connect it to the magnet. You want this to be a cold solder joint, not a hot solder joint.
Step 3: Hot Glue and Thumbtacks
Since everything is soldered now, you only have a little further to go until your LED module is functional. Take the hot glue gun and glue the magnets down on their sides. There isn't much need to worry about killing the magnets here since the glue gun doesn't transfer nearly as much heat to them as the soldering iron. Wait for the glue to harden before attempting the next part.
Once the glue has hardened, take the module, set it next to the speaker wire, and mark the wire where the center of each magnet would come in contact with it. This is where you'll need to insert the thumbtacks on the wire. Make sure they pierce the conductor inside the wire. This isn't easy to mess up, but if you're paranoid, you can check with a multimeter to ensure conductivity. Make sure that each pair of tacks doesn't go into the same conductor. This is how the modules are powered, and if both tacks go into the same conductor, that module won't work.
When you have the spacing right, you can use the thumbtacks you just put in as a template for the rest of the wire and since they have such a large surface, there's plenty of room for error. Another plus is that there is no need to have nails in the wall for it. Just hammer the tips of the tacks into the wall!
Now that you have your thumbtacks in your wire, connect the 12V supply and attach the module to a pair of tacks. If it doesn't work, try turning the module around. Reverse polarity won't hurt it. If it still doesn't work, make sure your connections are good between LEDs and specifically, between the resistor and its magnet.
Shown is a closeup of a working module and my hallway in near daylight. If you want to make a red module instead of a green or blue, substitute the three blue or green LEDs for 5 red ones and the 100 ohm resistor for a 1 ohm resistor.
Step 4: The Final Product
Here is a night view of the final product of this project. This, in addition to the kitchen half of the lighting, only pulls 1.26A of current. This means my power supply is only at 1/4 capacity! I could easily double the number of modules and cover the rest of my apartment, not to mention the possibility of ice sickle style modules. The real beauty of this comes into play if a module ever burns out. There's no way it can affect the remaining modules and you can just pull it off the wire to fix it. Burnouts happen at a very linear rate, where the Christmas lights burned out at an exponential rate. I haven't had one burn out on me yet.
Surprisingly enough, this project only took about 12-15 man hours to complete including all the LED module and rigging the speaker wire with thumbtacks. With help from my friends, we got all the leads coiled, magnets glued, and wire pierced in a couple hours. The cost was a little high, but I'd say $100 is a great price for lighting you won't have to replace for a decade or so.
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