For those of you who do not know, the joule thief is a very easy way to suck the remaining energy from "dead" batteries and use it to light an LED that would not normally light up when connected to the battery. In this Instructable, I will show you how to make a small joule thief lamp that can illuminate a good portion of your room while simultaneously taking away your excuse to throw your batteries away the second they stop powering your television remote!
Step 1: Supplies/Stuff You Need
Throughout the course of this build you will need the following supplies/tools
-NPN general-purpose transistor (I used 2n2222As. Despite what is in the photo, you only need one)
-Inductor toroid (I purchased fiftey of them on Amazon, but you can salvage small ones from CFLs)
-1k resistor (Most values will work but the resistance needs to be fairly low)
-Film canisters (You can get them on Amazon)
-Magnet wire (Mine is 24 AWG)
-Thick uncoated wire (The stuff I have is marketed at the Home Depot as picture hanging wire)
-Hot glue gun
-LEDs (Mine are jacked up from a previous project, but that doesn't matter)
-Hot glue sticks
-Perfboard (must be cut small enough to fit into the film canister)
Step 2: Preparing the Canister
Begin by using one blade of the scissors (or an Xacto knife) to pierce the lid of the film canister. The hole should be big enough to allow wires to pass through. After that is done plug in your hot glue gun. When the glue gun is heated up, put four dots of glue, all in a box shape, on the bottom of the canister. The globs should be fairly large and should be the same hieght. The globs will act like feet and will stop the device from sliding. To ensure that the device stays on whatever surface you keep it on, you can fold some electrical tape into a pillow and stick it between the feet.
Step 3: Wind the Inductor
To do this you will need two lengths of wire and a ferrite core. The core can be found in CFLs if you do not have one, but salvaged cores tend to be small so you will need smaller wire. The strips of wire need to be the same length. An easy way to ensure this is to take one long piece of wire and fold it in half. Now you can wind the wire in and out of the core. You can put as many windings as you want, but I am using eight. After you finish the process the core should have wire wrapped entirely around it. At the end of one side of the inductor you will see the fold of wire used to create the two ends. Cut across it with scissors to create two wires. Afterwards, scape off the coating of the magnet wire with a scissors blade (the better way to do it is with sand paper, but if you don't have any just use scissors).
Step 4: Prepare the Electronics
If you have knowledge of schematics, just follow the (crudely drawn) circuit diagram above and you will be just fine (note: the transformer shown is just the torroid). If you do not have experience with schematics, here is what you need to do:
-Find the pinout of your transistor
-Find the ends of each coil. You can do this by looking closely or by running a continuity test.
-Use a sharpie or simaller permanent marker and mark the corresponding ends of one of the coils.
-Establish which leads are the beginings and ends of your coil (THIS MATTERS!)
-connect the top end of the coil that doesn't have sharpie to the base of the transistor and solder.
-connect the bottom end of the non-sharpie coil to the 1k resistor and solder.
-connect the junction you just formed with the wire and the resistor to the top end of the coil with the sharpie on it and solder. Note that you may have to sand down the sharpie to prevent it from interferring with the electrical connection.
-connect the bottom end of the sharpie coil to the collector of your transistor and solder. Note that you may have to sand this connection as well.
-Connect two wires to your emitter
-connect a wire to the junction between the resistor on the coil wire
-connect a wire to the junction between the collector of the transistor and the bottom of the sharpie coil
After you have followed all of these steps, test the circuit with a dead battery as a power source and an LED. put the battery between the resistor wire and the emitter wire. Put the positive of the LED to the collector wire. If the LED lights up the circuit works.
Step 5: Installation of the Circuitry
Next use hot glue to connect one end of the board to the bottom of the film canister. All wires should be bent upwards. Before glueing it is best to label what wires are the input and output. After the board is glued, pull all of the wires through the top of the film canister. Snap the lid onto the canister.
Step 6: Installation of the LEDs
The LEDs in this project will be wired in parralel. To wire them this way, cut two equal lengths of thick, uninsulated wire. Bend the wire so it has an appearance of an "L". The bent portion should be around an inch long. Use hot glue to bind the one-inch side to the top of the film canister. The wires should be glued beside the hole, each wire being on the oppisite side of the other. Connect the output wires from the joule thief to the uninsulated wires. Solder them on and cover the connections with hot glue. Afterwards put a band of electrical tape above the connections to stop the wires from moving far apart. Now touch the input wires to the battery. Use an LED to determine which unisulated wire is positive. When you find out, begin twisting the LED leads to the wire.
Step 7: Dealing With the Battery
Naturally, the battery is going to be the most awkward part of this device. I used the gap between the two output wires to hold the battery in place. To create the battery contacts, cut some wire and connect it to the joule thief input. Tape the contact wires to the side of the film canister and bend them to the battery. If the contacts touch the battery the device should light up.
Step 8: Last Piece: the Reflector
Although this step is technically optional, the reflector can help focus the light. When you are reading a book, chances are you want the light directed towards you, not the cieling. To ensure that the light reaches you, first cover both LED leads (the "L" shaped wires) in electrical tape. This is nessasary to isolate the wires from the reflector. After this is done, cut a strip of aluminum foil. Apply hot glue to the electrical tape and place the foil, shiny side down, onto the hot glue. Bend the foil around the edges to further direct the light. This should ensure that you are getting as much light as possible.
Step 9: Conclusion
In this instructable I showed how to make a simple reading lamp powered by old batteries. This particular version was not built with details in mind; it is crude, prone to tip-overs, and probably not as powerful as it could be. However, it does prove that a simple lamp can be easily made with common household items (all electronics excluded, of course). It is possible I will find a circuit that draws more energy and looks more aesthetically appealing.
That's it for this Instructable. If you liked this, be on the lookout for more Instructables by me.