I'm on vacation right now at a lakeside cabin with my family, and the other night we thought it'd be fun to do some night swimming. It was indeed fun, but it occurred to me that it would be even more fun if I had some sort of glowing, floating thingymabob to throw around. So I ran inside and grabbed a cheap USB power bank that had a light and a waterproof plastic box, combined the two, and chucked it in the lake. As it turns out, cheap lights don't much appreciate being bashed around inside plastic boxes and this one simply gave up and broke into pieces. It was then that I decided that I'd scavenge around and create some other sort of floating, glowing thingymabob that wouldn't break into pieces. So the next day I hunted around the house, we're on vacation so this isn't our house and I don't know where anything is, and found a few supplies I thought might work. Then I thought that it'd be a good idea to make an Instructables detailing the build of my cheap, scavenged, and quite ugly I might add, LED floatie. By now I'm sure you've figured it out, this is that Instructable. ;) So tag along if you're cheap, broke, or just don't have much to work with but want to build a floating, glowing thingymabob anyway!
Step 1: Materials
Since I don't have much to work with, the materials will be very standard and I think just about any house you're at should have them. The only thing that may be tricky to find is the LED, I happened to have a bunch of them with me so I used some of those, but I did find one LED inside and old broken light. Try to find things like broken garden lights, flashlights, or electronics that might have LEDs inside, any color will work, but red may give you some trouble, so try to avoid those if possible. The materials list, along with possible substitutes for each, is as folows:
1. LED, any color, try to avoid red, and it needs to have leads (wires) on it.
2. Scotch Tape, any kind of tape will work, duct, gorilla, electrical, etc.
3. Hershey's Kiss, I didn't have aluminum foil so I used to wrapper, you just need something conductive, so a wire or aluminum foil works great.
4. Plastic Gallon Bag, or just any size plastic bag, but it needs to be water proof, so no holes. I doesn't need to zip, mine didn't, but it won't be a problem if it does.
5. Fishing Line, or just string of some kind, you'll probably want something stronger than thread, but you could get away with using thread.
6. 2 AA Batteries, or AAA, or C, or D (if you want a big floatie), or a coin cell or some watch batteries, or any combination of those. Basically you need two 1.5 volt batteries or one 3 volt battery.
As you can see, the materials are very flexible and you should be able to scrape up everything you need from around the house. Just make sure not to use anything you shouldn't if it's not your house. Also, you probably noticed that there's two of everything in the picture, that's because I'm making two of these, a blue and a green.
Step 2: Make the Battery Pack
Since an LED requires around 3 volts to light up decently, and AA batteries are only 1.5 volts, we need to put two batteries in series to get the 3 volts needed. Series means that the positive of one battery is connected to the negative of the next battery, so the two batteries act like one battery with the voltage of the two combined. Check the simple schematic above if this doesn't make sense.
To make the battery pack, we first tape the two batteries together, with the + of one battery next to the - of the other. Then we carefully unwrap the Hershey's Kiss, trying to do a better job keeping it intact than I did. Next, we take a strip of wrapper, or foil, about two inches long and fold it in half. Using a piece of tape, connect the battery terminals on one end with the strip of foil. Finally, use some more tape to secure the foil on the batteries well, we don't want the foil to fall off. We now have a 3 volt battery pack with one end covered in foil and the other end with two terminals. You can now tell people you have made your own battery packs, just don't go into too much detail or it loses its impressiveness. ;) However, if you'd like to actually make the floatie, move on to the next step, it gets even cooler than this.
Step 3: Connect the LED
LEDs, or Light Emitting Diodes, are really nifty little devices, they are a type of diode, which means that electricity can only flow in one direction across them, Anode (positive) to Cathode (negative). When the electricity flows in the right direction, they light up, glowing brilliantly with a variety of possible colors. Since LEDs are generally rated for voltages of about 3.4 to 3.6 volts, and our battery pack is only 3 volts, we will actually be under driving the LEDs. This means that they will be a little dimmer than they could be, but it also means that we don't need any resistors or LED driving circuitry to protect the LEDs, making it a very simple circuit. But remember, LEDs need to be connected the right way, or they won't light up. Using the diagrams above, figure out which of the leads (wires) is the Anode and which is the Cathode. The Anode will go to the positive of the battery pack and the Cathode will go to the negative.
Take a piece of tape and fold it over on itself, so that you get a plastic strip, then cut a thin strip of the tape and hold it on the negative of the battery pack. Place the Cathode of the LED on this plastic strip on the negative terminal, and place the Anode on the positive terminal. Use a piece of tape to secure the LED to the battery pack. The LED should not be lit right now, to turn it on, simply pull the plastic strip out from between the Cathode of the LED and the negative of the battery pack. You may want to test the light to make sure it works at this point. To turn it back off, just pull up the tape holding the LED in place, put the plastic strip back where it was, and reattach the LED to the battery pack. Now you may be tempted to chuck it in a lake at this point, but, although it will glow nicely, it will just sink and ruin the batteries, but it would look pretty doing it. The next step will make it water proof.
Step 4: Make It Float
We know that batteries sink because they're heavier than water, so in order to make the LED floatie actually float, we need to add something that is lighter than water, something like air. Since we need to make it water proof as well, an inflated plastic bag is ideal. If we put the LED and battery pack inside a plastic bag, then blow it up and seal it off, we'll get a floating, water proof container for our LED and battery pack.
First, we need to turn on the LED, since there's no way to turn it on or off from inside the bag. Then we cut the corner off of a gallon plastic bag, or use a whole sandwich or snack bag if you have those, just make sure it's big enough to hold the LED and battery pack along with some air. Now we stick the LED and battery pack inside the plastic bag, blow it up, and tie it off with the fishing line, or whatever string you have. Make sure to tie it tightly, and you may want to tie it twice, that's what I did, just to make sure it's air tight. We now have a floating LED floatie that's ready to conquer the Seven Seas, or lake or maybe just a puddle, whatever it may be.
Step 5: Testing and Trouble Shooting
If all went well, you should have a nice, super cheap, kinda ugly LED floatie. Go ahead and test it out in a bathtub or sink to make sure there's enough air in the bag to make it float. If it floats, then you're done!
If it didn't work, don't panic, pull out your hair, or chuck it in a lake anyway, just check this short list of possible issues:
1. Is the LED connected the right way? Try taking it out and flipping it around.
2. Are the batteries dead? If you picked up some random batteries laying around like I did, they may be dead, so the LED might not light up or it might light up really dimly.
3. Is the foil in the battery pack making good connection? If it isn't, the battery pack won't work properly, so the LED might not light up, or it might flicker on and off randomly.
4. Is the LED burnt out? LEDs can burn out after some time or if they're abused, if you pulled the LED out of something old or broken, it's possible that the LED it broken too. Try another LED if you have one.
If none of these fix the issue, try getting all new supplies and making another one.
One last thing, always make sure you pick these up after you use them, don't leave them in the water, not only can you reuse them, but it's littering to leave them around, which is both illegal and irresponsible.
Now go! Go forth and have a party with your new glowing, floating thingymabob, or make a bunch more and have an EPIC party!
Edit: Don't actually throw them anywhere, they are apparently not very durable, which I guess should have been obvious.