Joule Thief FlashlightA cool LED flashlight with an ultra long battery life.
Step 1: Winding The Coil Step 2 of 6
In this step, you will wind magnet wire around a nail, or nut and bolt. Make sure the nail or bolt is magnetic! If it is not magnetic it will not work! The coil will be about 1 inch long when finished, so use a bolt that is about 1 inch or so. If the nail/ bolt is too long, you can cut it with a hacksaw before you wind the coil.
Take 25ft of enameled magnet wire, and fold it in half, so that there is a loop and 2 free ends on the other side. Next, place the loop side near the flat part of the nail, leaving about 2 inches of extra wire on the loop. Now wind the coil, and make sure it is about 1 in long. Leave about 2 inches of the two remaining wires when finished.
The finished coil should look like this:
(Notice the loop by the flat end of the nail):