In my first Instructable, I created a portable LED flashlight out of a circuit board, a couple cell phone batteries, and a few bright LEDs that I ordered off the internet. Bright and easy to make, it was a nice, simple flashlight. However, I designed it with the intention of soon building a far more powerful version - that is, if I ever had the time to order some brighter bulbs. Well, a few days ago, those 1 watt LEDs arrived, and I was able to construct a new light that put my old one to shame.
Step 1: Parts and Supplies
For all its power (this is a blindingly-bright light), it actually doesn't cost very much to make. In fact, discounting any tools you might need to buy, supplies for this project will likely run from $10-$25. Below is a list of all necessary materials, along with their potential price ranges.
1. 12 high-powered LEDs. These bulbs must be rated for between 3 and 3.4 volts, and should be no less than 1/2 watt. The ones I bought require 3.3 volts and are designed for 1 watt of power. ($3-$10)
2. An aluminum heat sink. Given that this light may be handling between 10 and 15 watts of power, a metal surface is necessary to dissipate excess heat and prolong the life of the LED bulbs. As a rule of thumb, your piece of aluminum should be at least 3 inches wide and long. ($0-$5)
3. Extra wire. In order to link LED strings together, you will need to attach them using copper wire. The wire should be very thin and malleable so as to avoid twisting and damaging the metal tabs protruding from LEDs. ($0-$5)
4. Soldering iron and solder (Variable)
5. Superglue ($1-$3)
6. Paper (Negligible)
Step 2: Preparing the Aluminum Heat Sink
The aluminum heat sink will form the centerpiece of this project. Because the LEDs being used here are capable of serious power, they will generate large amounts of heat, most of which will need to be drawn away and dissipated. While it is possible to build atop something other than aluminum, the heat buildup would definitely result in decreased performance and a drastically-shortened lifespan.
To kick off the project, start by marking out where you will place your individual LED bulbs. I chose to go with a 4.5 by 4.5 cm grid, with points every 1.5 cm. You may choose to set your LEDs in any location you see fit, as long as they will all fit comfortably on the heat sink. For best results, you will want to position your bulbs close enough to each other that their metal tabs will touch, yet not so close that they will be packed together. Ensure that all 12 points are marked, one for each LED.
Step 3: Prepping the LEDs
In mint condition, the high-powered LEDs should have two terminals. Begin by determining which are positive and which are negative. You will need to connect them end-to-end, with positive terminals linking to negative ones. Additionally, you should notice that your LEDs have a metal base on their underside. This metal base is intended to be connected to the heat sink. It is not a terminal.
After you have identified the positive and negative tabs, use a pair of pliers to gently bend them upwards as shown in the picture. This is to ensure that they do not contact the aluminum surface, which would cause a short circuit. Line up your LEDs on the spots you've marked, making sure that they will fit comfortably once secured.
Step 4: Putting It All Into Place
Once your LEDs and your aluminum heat sink are ready to go, it is time to begin gluing! In the spots you designated for your bulbs, drop a TINY amount of superglue. This is deceptively tricky, as too much glue can coat the heat-dissipating base of your LED or, worse yet, the tips of your fingers (which sucks!) Once the drop of superglue is in place, lower the bulb onto it and press down on its top with moderate pressure. Depending on what type of glue you use, you may have a couple seconds to 'slide' it around into the perfect position before it is stuck for good.
Before you glue an LED down, always check to make sure that its polarity is correct. We will need three strings of bulbs, with each individual 'string' consisting of four LEDs placed in series. This means that we will connect them negative-positive, negative-positive, etc. It is absolutely crucial that each string is connected in the same way, with all positive tabs on one end and all negative tabs on the other. If just one of them is accidentally installed wrong, it will cause an entire string to not work, and since superglue is almost impossible to remove, it is very wise to "measure twice, and cut once" here.
Step 5: Soldering and Wiring
After gluing and setting your LEDs in the right positions on the heat sink, we can turn our attention to soldering it all together. Because the LEDs have been placed right next to each other, this should be a fairly straightforward process. Simply solder every pair of leads together, making sure that each joint is secure and well-placed. After this is complete, you should have three separate rows of LED bulbs, each one connected in series.
Throughout this step, you will want to be conservative with the amount of solder you use. The LED terminals will, in all likelihood, be hovering less than an eighth of an inch above the aluminum surface of your heat sink, so any solder that drips down onto the metal will need to be removed. Additionally, these LEDs are (as the need for a heat sink attests to) very sensitive to high temperatures. Because the heat from your soldering iron will conduct quickly through the metal tabs of your LEDs, you should strive to get the soldering job done as quickly as possible to avoid any potential damage.
Once your rows have been created and all your soldering joints are cooled, link the three leads on each end of the rows together by connecting them with thin, malleable copper wire. These connections should be secure and tight. As you do this, take care to not excessively bend or break the fragile LED tabs. When the copper wire is in place, cut out thin slips of paper and superglue them to the metal underneath both rows of wire, as shown in the photo above. This will create an insulating layer between the heat sink and the copper, thereby protecting against a short circuit. For good measure, you may solder the copper-LED tab junctions, making for a more permanent connection.
As a last step, attach insulated wires to the ends of the copper wire strings, thus giving your new LED light a way of connecting to batteries and power sources. It is now almost ready!
Step 6: The Finished Product
With the LEDs set up and the wiring complete, the only thing left on our checklist is to figure out how to power it. Because this is a 12 volt system (or 13 volts, to be more exact) the possibilities are almost endless. Car batteries, lantern batteries, solar panels, wall adapters, etc. would all work well. In my case, I use two 6-volt rechargeable batteries wired in series. They put out 12.6-13 volts when fully charged, and this level of voltage is almost perfect for the application.
Before you attempt to power this light, however, you should be wary of its power-handling capabilities. Each LED in my array is rated for 1 watt, and with 12 LEDs in total, the overall power consumption should be around 12 watts. Using a 12 volt source, this works out to a current supply of roughly 1 amp. This is critical, as unlike incandescent bulbs, LEDs cannot limit the amount of current passing through them. A failure to control the amount of amperage supplied to them would be catastrophic, possibly going so far as to burn out the entire array in short order. Therefore, some level of resistance is needed to make sure that the current doesn't become too high for the LEDs to handle. Assuming your power supply is somewhere between 12 and 14 volts, this resistance will be roughly 10 ohms.
There are many ways to go about solving this problem. Perhaps the most fitting solution would be to buy a power controller online, as these are fairly inexpensive and many of them are able to adjust the amount of energy reaching your LEDs, thus acting as a brightness adjuster. However, for those looking for a quicker fix, a resistor can be made out of any number of items. Below, I will detail a few of them.
1. Motors. Because they make use of the attractive and repulsive forces of electromagnets, all motors (AC and DC) have coils of copper wire within them that contain hundreds or even thousands of feet of wire. Although copper is highly conductive, it still has resistance, and this resistance only builds up as the wire lengthens. Generally, I have found that small DC motors have resistances of around 1-5 ohms, while larger AC motors can have values as high as 30-100 ohms! If you have a multimeter capable of measuring resistance, you can experiment with different motors to find out which ones work best. Remember that, while a 12 volt battery would require 10 ohms of resistance, a higher level of resistance can't damage your light (other than stop it from being as bright as it could be). I have an AC motor which, due to its huge amount of fine wire, registers as a 30 ohm resistor. With my 12 volt power supply, this translates into a roughly 0.3 amp power yield, which means that the LEDs are 1/3 as bright as their maximum. This level of light is still more than sufficient to illuminate an entire room.
2. Enameled copper wire, also known as magnet wire. If you have some of this on hand, it could be your ticket to quickly improvising a resistor. Generally, smaller wire works best (28 gauge or thinner), and, by wrapping it around something non-conductive, you can create a relatively small resistor with a value of between 5 and 15 ohms - perfect for this application. Resistors built in exactly this manner are actually sold commercially, and are known as wire-wound resistors.
3. Pencil lead or graphite. If you happen to have access to pencil leads or graphite cores, you can create a variable resistor. Attach one end of the rod to your LED bank, and then, at the other end of the rod, connect your power supply. By adjusting the distance between these two connections, you can change the resistance, and thus, the brightness of the LEDs. Note: mechanical pencil leads do NOT work well.
After you have made an appropriate resistor (or gone ahead and bought a commercial LED controller), your light is ready to use. It can be bolted to a fixed frame, made into a flashlight, attached to a solar power system - the possibilities are endless! With 10-12 watts of total power, the LED light array will be capable of producing the same light as a 75 watt incandescent bulb. With this much in power savings, you'll find that this easy-to-make light is not only incredibly rewarding, but cost-effective as well.
Thank you for reading!