Joule Thief 101

[MileHigh]

Smoky2:

I am trying to bring everyone up to speed on this, because once we all get it, we can go to the next level.

If people are still getting hung up on the very basics, we must communicate the information more effectively.

Simply put, once the JT is operating at a resonant frequency, we can remove the LED/load completely,
and couple to it, using the inductor as a transformer. By winding a secondary onto the ferrite.

With an appropriate capacitance, this secondary coil can be set resonate with the frequency of the rest of the circuit, and used to power a load.

I am all for that because I am all talked out about this.  The proof is in the pudding.

Not to be too cynical but often you see experiments around here that are all about a "new way" to power a load.  The catch is this:  Can your circuit outperform two wires?   Of course I am oversimplifying but I think you get my point.

MileHigh
   

[MileHigh]

Smoky2
Thanks for the helpful explanations. I think the direction with a secondary is where Jeanna was going some years back. She had some YT videos using multiple secondaries - very interesting stuff.  IST had a slightly different approach, and often used a kind of caduceus winding for his multiple secondaries. 
Looking forward to a more purposeful kind of build that would enable us to produce the resonant effect and draw from it.
Bob

All of Jenna's clips about this were just an exercise in experimenting with a transformer with multiple secondary windings.  How does a transformer distribute power when there are multiple secondary windings wiith different numbers of turns and perhaps each secondary is driving a different value of resistive load (or different LEDs)?

This is a basic nuts and bolts transformer question that any serious electronics hobbyist should try to answer for themselves.  When Jenna did this there was never a manifestation of extra power.

[Magluvin]

Smoky said...
"I think what you will find, is that in most set-ups, the LED itself never fully turns "off"."


With a standard Joule Thief circuit the LED does switch off so the persistence of human vision does come into play.  I do appreciate how you stated that the persistence of human vision is a complex process and not necessarily a one-size-fits-all proposition.

MileHigh

With the led across the driver coil, not the trigger coil, the inductor collapse winding down could possibly still be passing current(and light output) through the led by the time the transistor is triggered again.  Also white leds have phosphorous that has a persistence of emission also.


Mags

[tinman]

With the led across the driver coil, not the trigger coil, the inductor collapse winding down could possibly still be passing current(and light output) through the led by the time the transistor is triggered again.  Also white leds have phosphorous that has a persistence of emission also.


Mags

The LED will be off during the on time of the primary coil,as the voltage is inverted across the coil during the on time,and that voltage cannot exceed the voltage of the supply battery. You could of course use a diode and cap with an LED across the cap,and it will be on 100% of the time.


Brad

[seychelles]

as always i will give away my top secret coil winding system..check it out..the winding is in bifilar configuration..