Joule theif : try out !

[TinselKoala]

Sorry... just trying to be helpful.

http://www.youtube.com/watch?v=zM1qdATaiks

http://www.youtube.com/watch?v=CFEr4o3sp7U

http://www.youtube.com/watch?v=tuFWC-yyIyU

http://www.youtube.com/watch?v=MeIWpkywGXs

[Farmhand]

Thanks guys, I went with the basic joule thief with an adjustable resistance and the diodes from ground to base.

Just for a laugh I decided to setup a galvanic cell in a small bucket and using a couple of carbon gouging rods (copper coated) for the positive and a too small piece of zinc plated steel, a bigger zinc plate would work better.

I get only 0.9 volts open circuit and powering the joule thief it works in a "burst mode" "charging two AAA's" as the shots below show. It seems to start to oscillate at about 0.4 volts or so but the joule thief draws down the voltage until it stops oscillating then the voltage builds again. The frequency of the bursts appears to be 25 Hz going by the scope and the RMS voltage shown is about the same as the open circuit voltage of the gal cell  The batteries are gaining voltage

EDIT: Correction now I look at the time base and the bursts are between 1 and 2 Hz I think.

I'll add a tiny bit of magnesium sulfate to the cell.