Boards. Make a Joule thief. In the November 1999 issue of EPE (Everyday Practical Electronics), a small and intriguing circuit was published in the Ingenuity Unlimited section by Z.
Kaparnik. It was a very small implementation of a typical transformer feedback single transistor invertor. The transformer was a standard ferrite bead with two windings wound on it and the circuit was using the high voltage pulse generated when the transistor turns off to light an LED from a single 1.5V battery. This page has two variations on the original design to use the simple circuit in a useful manner. I originally called this torch the vampire torch because it sucked the last remnants of life from a cell, but then decided to call it a Joule Thief instead because it was a catchy name and played on the fact the unit steals the last bit of energy from a cell.