Joule theif not working at 0.5 v ?

[omdano]

What MarkE said above is quite true.

For low voltage startup with a bipolar transistor,
either silicon or germanium, the base drive must
be adequate to assure that the transistor turns
"on" sufficiently.  This usually means that the
base current limiting resistor will need to be
reduced in value.

Or, some sort of switch can be placed across the
resistor to temporarily and briefly "short" it to
start the oscillator.  Once running it may continue
to run at the low voltage of 150 to 200 milliVolts
or even less.

In some very low voltage Joule Thief oscillators
the base resistor is not used at all.

so..  i guess i shall be playing with the base resistance in this circuit :

http://www.electronics-lab.com/blog/wp-content/uploads/2007/11/1828270262_b76c867954.jpg

to make it work :p (i am using 2n4401 instead)

[Vladokv]

Here is my joule tief with germanium transistor AC551.
http://www.youtube.com/watch?v=-KuDI2bFYN8&feature=youtu.be
Later I will post measurment of rectified output with and without _load led.

[omdano]

Here is my joule tief with germanium transistor AC551.
http://www.youtube.com/watch?v=-KuDI2bFYN8&feature=youtu.be
Later I will post measurment of rectified output with and without _load led.

<3 you

[SeaMonkey]

so..  i guess i shall be playing with the base resistance in this circuit :

http://www.electronics-lab.com/blog/wp-content/uploads/2007/11/1828270262_b76c867954.jpg

to make it work :p (i am using 2n4401 instead)

Aye, that is how you'll get it to start and
run at the very low voltage.  The transistor
type should not be too critical since nearly
any small signal transistor with a current gain
(Beta) of 100 or better should work well.

[Vladokv]

http://www.youtube.com/watch?v=slGX1GUXd6o&feature=youtu.be
video shows max. voltage of unloaded joule tief.
Suprisingly, white led works with only 2,6v.
I have expected more