Small 1.5V to 5V or 12V DC/DC converter with LT1073 chip. The IC is available in three different versions, depending on output voltage. Two with fixed output voltage of 5V and 12V, and the most interesting that can be adjusted. The adjustment is done through a voltage divider with two resistors, of mass, output and Terminal 8, internally connected to the voltage comparator IC, which is responsible for stabilizing the output voltage.
LT1073 has an internal everything you need to make a small DC / DC converter with a low operating voltage of only 95μA 1V and consumption without load.
If you do not have a meter inductance, the inductive part of the drive is a bit more complicated to make, but we shall see some possible solutions. Capacitor also recommended by the manufacturer for the circuit is a bit hard to get, I have used a tantalum recovered from another power source, and the ripple voltage at the output is quite low. Last but not least, say that the diode has to be a fast, not worth as the 1N4002 rectifiers, the 1N5818 is recommended schottky type, characterized by high response time and low internal resistance, which is what ideal for this type of converters.
As we can see from the photograph of the circuit in a low energy lamp, ay a small toroidal core can be recovered. 82μH To this core, we winding 7 turns of 0.3mm enamelled copper wire.
Another option is to use a toroidal core Ferroxcube, Farnell code 178-504 of 13.25 x7, 35x5, 7mm, grade 3C85, value AL 1000. with this core we have winding 8 turns to 90μH.
Finally, note that you can download the documentation in the manufacturer's website, is very good and complete, with numerous examples of applications, and above all very clear.