Joule Thief

[dasimpson]

noted that all my joule thiefs start at around 10 ma at 1.25volts just need a way now to ajust the voltage so i can see what voltage they will start at these are dimly lit btw i need to find a whay to get the full brightness yet

this informatin should then tell me what i need from my earth battery

[dasimpson]

my new toroid winding not sure what wire im going to use for the secondory winds what ever i can solvage i guess im hopeing to get 80 winds per side

[jeanna]

noted that all my joule thiefs start at around 10 ma at 1.25volts just need a way now to ajust the voltage so i can see what voltage they will start at these are dimly lit btw i need to find a whay to get the full brightness yet

Nice toroid. It has a familiar look.
almost anything will work for the secondary winding.
If it is thinner you can fit more turns but the wire is brittle and you can get failures just from that.

May I suggest that you get a potentiometer?
Allelectronics has a 1k pot which I use a lot Sometimes you get a lot more out when you have less than 1kr at the base.

=======

@all,
I want to report that the oscillation enhancing cap I added across the secondary last night has continued to work for over15 hours.
I arrived at the number by using a calculator.
The freq of the joule thief = 333khz
the inductance of the secondary wire around the toroid = 1.6mH
the resonance is predicted when a cap of 140pF is added.
And it worked.

The reason I never tried this before is that the calculator is for a different kind of oscillator circuit.
anyway this worked.

I used 68pF which worked for about 15 minutes, then the light went out. It started up soon after, but it would not stay constant.
The 220pF killed the light.

So, I am reporting this because I think it is an important lead in what to do with the spiky output volts.

@jadaro, BTW the cap makes this output into a smooth sine wave.

I hope some others will try to enhance their output.
http://www.whatcircuits.com/lc-resonance-frequency-calculator/

Maybe the circuit is the same if I turn my head. mmm 

jeanna

[dasimpson]

yeah i have been messing with a 45k pot today my new wound toriod i put 10 winds secoundry on and  a bridge rectifier i got 180volts can not get the 180 again but sits at about 160volts only problem with that is im kaeking 100ma from the battery to get that voltage im going to put a pot on my battery set it to max draw 10ma buy using my meter to mesure the amps and slowly turn the put till i get what i wont im then going to try more and less winds secondry to see if i can get the light brigter

[dasimpson]

any idea on how i could control the voltage ?