This piece of oak serves as a quick way to swap parts for a Joule Thief.
I have an air core coil connected to it, and a 3mm white LED which is tired from being used for a few hundred hours. The plus and minus wires are each wrapped around a steel screw and the nut is tightened to hold the wire. Then neodymium magnets are used to hold the screw to the battery. The positive end of the AA cell grabbed the positive screw in the board so I left it there.
The piece of paper attached to the coil said that it was ten feet of 24 AWG solid telephone wire and 32 microhenrys. Thatś kind of low for a JT, but it´s working. The transistor is 2N4401.
Where is the circuits, How can I build it?
You can search for Joule Thief and click on the Wikipedia wiki for the schematic. You can build it as I showed with a piece of wood and screws. The transistor is a 2N4401.