Introduction: {THE LED LIGHTBULB}

About: I am an undergraduate at the Massachusetts Institute of Technology, where I intend to study Electrical Engineering and Computer Science. I am a tinkerer by nature: above all, I love to learn by building, wiri…

With energy at shortage, we strive to conserve. Although we attempt to buy the greenest electronics and turn them off as much as we can, we still find ourselves with those energy wasting incandescent bulbs or those mercury infested CFLs. The immediate solution that comes to mind to switch to LED light bulbs, which is then stricken down by the fact that LED spots are still at an extremely high price, making it cost a fortune to convert over all of your existing fixtures to this technology. But this is instructables, so we can make our own! What we will end up with is one of the most energy efficient light bulbs you have ever had in your midst, made at a ridiculously low cost. This will save you $100s of dollars throughout the lifetime of the bulb; so feel free to write me a check for the calculated amount!

Step 1: [SUPPLIES]

With LEDs at such high costs, you must know a tremendous supplier. I ordered most of my supplies from two main sources, LED Shoppe and All Electronics. I have found these suppliers to be the cheapest and most reliable. I ordered a large quantity of supplies, since I am going to make several bulbs of various sizes, which made the supplies cheaper. Below are the list of things I needed for this project:

LEDs - I used 5mm LEDs. You can change the type of LEDs as long as you augment the calculations accordingly.
Bridge Rectifier - Converts AC to DC.
Perfboard - The size of perfboard you buy will depend on the size of light bulb you wish to create.
Soldering Iron and Accessories - The cheapest of soldering irons will do.
Base Plug - This product has a normal bulb's base at one end and a normal household outlet on the other. Your local hardware store will most definitely have some.
Cable Ties - The question here is not if you have them, but, rather, how many hundred of them do you have.
Cardboard - This is the main support piece for all the component of the bulb.
Wax Paper - I used a silicon cookie sheet (that rolled up blue thing) instead. You can use practically anything that has a high temperature tolerance and doesn't conduct electricity, but I have found these to be the best materials for the job.
Drill and Small Bit - I used a 1/8" drill bit.
X-ACTO Knife and Whole Puncher - These items will be used to prep the insulation.
20AWG Wire and PVC Pipe - These are required to connect the bulb's base to the rest of the assembly.
Multimeter - I always keep my multimeter handy in order to check conductivity and make sure there are no shorts.


Now, like any project with electricity, certain calculations are necessary. Although the equations might look a bit threatening, I can assure you that it's quite simple. Before starting your calculations, make sure you have your LEDs' detailed specifications from your supplier.

FV (Forward Voltage) - This is the voltage used by each separate LED. It is expressed as a range, so a minimum and maximum value is present.
AC MAX/MIN - AC Mains are not always at a constant voltage and are not always the same across a whole house. There is actually a range present. In the US, the range is 110-125VAC. In other nations, the range is 220-250VAC.

[AC MAX] X 1.4 = A
A / [FV MAX] = [# LEDs]

[AC MIN] X 1.4 = B
B / [# LEDs] = C
C represents the forward voltage and must be within the range.

Your final result represents the number of LEDs you can put in each series. Think of this as a basic unit. The total amount of LEDs on the light bulb must be a multiple of this number. In each "unit," the LEDs connect positive to negative in order to distribute the voltage. All the series may then be connected together, positive to positive and negative to negative. Below is a sample of my calculations.

125 X 1.4 = 175
175 / 3.8 = 46

110 X 1.4 = 154
154 / 46 = 3.3478
C is in range. (exhale)


The insulation is made out of two layers. The silicon/wax paper layer sits right on top of the circuit board and comes in direct contact with the circuitry. The second layer is made of cardboard and sits atop the first layer. Besides being a layer of insulation, this layer is the physical center of the bulb and holds together all the components. I extracted the cardboard I used out of a binder, since I found it to be nice and dense. After you have your cardboard, plop the pieces of perfboard atop it and trace their outline/holes. I found that drilling the holes with your drill on reverse doesn't allow the cardboard to burr. When it came to cutting, I used a normal kitchen knife. (I cheated) Finally, I drilled a small whole a bit off-center and two holes, about an inch apart, on either side for mounting. The second piece of insulation is made of silicone or wax paper. Both work fine, but you must use at least two layers if you use wax paper and must have the glossy side facing the circuitry. Trace out the perfboard as before, but cut with normal scissors. As for the wholes, I used a special small hole punch. If you do not have one, then you can simply snip a small hole with scissors. In addition to the wholes at each corner, make one a bit off-center, corresponding to the one on the other layer of insulation, for the electrical wires to pass through.


What makes this a normal bulb is its base; it can fit into any existing fixture. You do have slight freedom with the base, however, since all fixtures are not created equally. The purpose of the PVC channel is to house the excess wire and give a bit of extra length if the fixture requires it. The one shown is made to be quite long for a specific fixture. The procedure for making the base is as follows:

1. Drill Holes - Make two small diagonal holes on each side of the base plug, in between the prongs. Make sure the hole starts at the outer edge and ends slightly inward, in order to ensure that these mounting holes do not interfere with the functionality.
2. Strip and Tin - Strip the wires and twist the strands together. Apply solder to the ends. (what we call "tinning")
3. Insert - Insert the wires into the holes and secure them with bits of plastic. If you want, you can also solder them in place with a very fine tip, which I do not posses.
4. Check - Set your multimeter to the diode check mode. Touch each multimeter probe to each wire end; nothing should happen. If your multimeter beeps, then there is a short somewhere, so you should check your work. Now, keep one of the probes on a wire end and touch the other to a contact on the base. There should be conductivity indicated on one and not the other. Repeat this for the other wire.
5. PVC - Cut your desired length of PVC pipe and drill holes in it. Attach the base plug to one end with cable ties. We will later mount the circuit board to the other.


I split up soldering into the following steps:

1. Plan - Place the LEDs in their approximate location. You will find yourself switching the locations of the LEDs in order for them to fit on the perfboard, so this step is crucial. Make sure you follow your calculations and use your results to determine how to place the LEDs. Keep in mind that they will be connected positive to negative in each series, and all the series will be connected together positive to positive and negative to negative. For example, I would connect 46 LEDs together, positive to negative, and then connect all the positives and negatives at each end together. At the conclusion of the planning step, I took a picture to remember where I had placed everything.
2. Place - Insert one row of LEDs at a time, making sure you are paying attention to polarity. Remember that the longer lead of an LED is always the positive one.
3. Bend - Bend each lead to the approximate soldering joint and cut off the excess.
4. Solder - Take this one joint at a time and make sure each is done well, since you are working with high voltages. Heat up the joint and apply solder between the iron and lead. Then, move the solder to cover the rest of the joint, using the initial solder to conduct the heat. If you need further help soldering, there are tons of online videos that will assist you.
5. Snip - Clip the excess leads, making sure to be gentle with the soldering joints.

Step 6: [ASSEMBLY]

Now that all the separate components are prepared, we can move on to assembling the whole bulb. Run the electrical wire through the center wholes of the two layers of insulation. Solder the wires to rectifier leads (labeled "~") and snip off the excess. Make sure that everything is soldered correctly before you close it up. Mount the PVC pipe to the cardboard with cable ties. Then, slowly pushing the wires into the pipe, sandwich all the layers together and secure them with cable ties at each corner. After checking that nothing is exposed, plug in the bulb to check if it works. Be extremely careful with this testing, as with the rest of this project. I am not responsible for any injuries, either physical or emotional. =]

Step 7: [USE]

Let the energy saving begin! When you are done, you can screw it into any light fixture and begin saving immediately. I put some in various places of my house and plan on making even more in the next few weeks. Though I went at this project with the light bulb method, you could make just the top portion and wire them together (don't forget the fuse there). That is what I am going to do and mount it above my desk. Also, these would be absolutely perfect for recessed lighting fixtures. In case you were wondering, I have summarized the cost for you below:

Small (46 LEDs):
Perfboard: $1.00
LEDs: $0.05 X 46 = $2.30
Wire: $0.18 X 1/3ft. = $0.06
Rectifier: $0.50
Base Plug: $1.00
Total: $4.86

Medium (92 LEDs):
Perfboard: $1.50
LEDs: $0.05 X 92 = $4.60
Wire: $0.18 X 1/3ft. = $0.06
Rectifier: $0.50
Base Plug: $1.00
Total: $7.66

Large (184 LEDs):
Perfboard: $2.00
LEDs: $0.05 X 184 = $9.20
Wire: $0.18 X 1/3ft. = $0.06
Rectifier: $0.50
Base Plug: $1.00
Total: $12.76
As for everything else, I had it all laying around.

I certainly enjoyed this project and hope you do too!

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