The Germanium Joule Thief

This little guy is a Joule Thief with a vintage 2N1307 germanium transistor. The transistor is PNP
and uses the same schematic, except the polarity of the battery and LED is reversed.

Germanium transistors have a lower turn-on voltage and allows this Joule thief to run a battery down to .2 volts.

 My blog page has more about the low turn-on voltage.

Ferrite is another Germanium Joule Thief.  Both of these artbots have a magnet on the bottom of the battery holder and is used to attach to a disc of steel.
On the top of the head is a CDS photo resistor that causes the leds to only come on in the dark. 

Link to PDF of the schematic showing the concept of adding a photo senser to the Joule Thief.