Joule Thief

[crowclaw]

@ crowclaw

Your scope shots are excellent. Would you be willing to post a dual trace shot with the CE on one channel and the voltage across the base resistor on the other channel? I do not have a scope so I can not do this, but I think it would be interesting.

Hi xee2,
No problem... I take it you want to see the base drive signal BE? as soon as I get a chance Ill post the pics. Regards

[xee2]

@ crowclaw

Hi xee2,
No problem... I take it you want to see the base drive signal BE? as soon as I get a chance Ill post the pics. Regards

The voltage across the resistor shows which way the current is flowing. I suspect that there is a reverse current that helps turn the transistor off quickly and is responsible for the large voltage spike across the coil (voltage = rate of change of current). The spike does not seem to be as large if the tansisor is driven with a square wave.

[jeanna]

http://www.youtube.com/watch?v=ZnNQrYy_Bw4
Tiny orange toroid slide show on youtube.

This time I checked it before I posted the address.
Sorry for last night's boo boo.

jeanna

[WilbyInebriated]

http://www.youtube.com/watch?v=ZnNQrYy_Bw4
Tiny orange toroid slide show on youtube.

This time I checked it before I posted the address.
Sorry for last night's boo boo.

jeanna

nice! you deserve a standing ovation.

[jeanna]

I noticed that loading the toroid on a tertiary causes effects, not sure how profound, but they are destructive on the derivative that I built.

I thought that, on a standard setup, with two driving coils and a large secondary, a small tertiary coil be incorporated.

The tertiary coil be three to four winds of copper, rather than attaching this to anything that creates light, it could have a varistor / potentiometer attached between it's leads which creates a shunting load - this may have the effect of an electrically isolated tuning apparatus.

This thought was inspired by IST's tuning coil mod, but it makes a simple effect and uses less equipment.

Not sure how useful this would be though, as the circuit goes into resonance as it already is, the idea would be tuning for both directions of the flux, as the potentiometer usually has three leads, an optimum could be set; using previous data - a diode on the middle lead, and have the other ends connected normally ..this would allow less resistance in one direction than in another and thus circulating pulses and magnetic fields could be experimented.

Red is the mod, green are the common coils to base and emitter, while blue is the secondary.

As is, the image is most basic in design, the idea would be to first find an optimum for each direction and incorporate additive or subtractive resistance as needed.

edits: had to sign it, been forgetting that lately. 

Try adding inductors with each light output. Add them in series.

If the inductance is close enough to the resonance of the main (green)  circuit, it will allow each light or light group to be not effected by the others on other winding.
I think I called this "multiple secondaries", and made a series of videos about it.

Enjoy that, but do try the inductors.
My experience says, once you get it right a cap will keep it going better, but get the inductor right first.

jeanna

edit
Thanks, wilby
-------------------

Here is a pic of those small toroid's found in CFL's this one is seen as removed and has three windings. What I have done is wired up as a JT without rewinding the coils. The yellow wind is left untouched. The scope screen PC shot shows the wave form, and the circuit was running at 1.5 volts  with a 10K adjusting pott. Frequency 158KHz. I just put this in for those new members who want to try the "Joule Thief" circuit out using scrap.

I guess we are on the same wavelength here, crowclaw!!
This is great information.
I had destroyed the shorter wires and could only reuse the longer one.
158KHz... wow!
10K pot.
This is so great.
And those scope shots. I agree with xee2. I would like to see the 2 trace.
Also if you wind a 10 turns secondary-pickup around that toroid and take a scope shot of that too. I would really like to see that too.
thank you,
jeanna