Battery-free LED Closet Light

Have a closet that's dark as the inside of a cow? Hate changing the batteries on portable closet lights? Don't trust yourself to install a proper light without electrocuting yourself? Then install a transformer - powered LED closet light!

It helps to have a soldering gun, but it's not strictly necessary.
1. LEDs; I used three 3-volt white LEDs soldered together, so that they ran off a total of nine volts.
2. 100 Ohm resistor; anything close to 100 will work. If all you have is a big bin of random resistors and no multimeter, just keep hooking up LEDs to various resistors until you find one that works.
3. Wall adapter; mine was a nine-volt unit from an old internet modem. You could theoretically assemble an LED array to run off virtually any adapter; you could use a whole bunch of LEDs and a higher voltage transformer to have a really good light!
4. Lots of wire; it should be thick enough to carry the current from your wall adapter; if you used a low - power one like mine, probably just about anything will work. You should have enough to go to the nearest outlet in your room - which, by the way, does not have to be inside the closet.
5. Something to diffuse the light; I made a serviceable shade out of a tissue, some adhesive spray, and a water bottle. I'll describe how later.
6. A switch; virtually any kind should work.

This is the main wiring part. First, determine what voltage your LEDs are and how many of them you need to run off the voltage from your wall adapter. then, solder or twist them together, in series, not in parallel. Add the resistor to one of the two input legs, make sure it works, and that's most of the wiring right there.

You need something to diffuse the light. I took a small plastic water bottle, sprayed it with 3M super 77 spray adhesive, and stuck tissues to the outside. Then, I drilled holes in the cap and threaded the LED wires through. I slid the LEDs through the mouth of the bottle and tightened the cap in place.

Attach two of your long wires to the LED wires coming out of the shade. Fasten the wires to your closet ceiling, or wherever you would prefer to put the light. Run them to wherever you want the switch to be and splice it into the circuit. I mounted it with foam tape. Run the wires down the wall and out under the door, if your wall adapter is somewhere outside the closet. Make sure you run them somewhere you won't trip over them, like through the corner of the door opening. Connect them up to your power source, making sure your polarity is correct. You can cut the head off the adapter plug and splice the wires in directly; I plugged it into the power socket from an old answering machine and spliced the wires to that.

Finished! Flip the switch, and the LEDs should turn on. if they don't, check that your power source didn't fry them, the polarity is correct, and, of course, that your connections are good. Now you can see what you're doing when you get up in the morning! And you never have to change batteries!