Joule Thief 101

[allcanadian]

@milehigh

So how can you get a "breakdown" in Ohm's Law?  It's nothing more than an observation of voltage and current for a device under test and defining the term "resistance" as the voltage divided by the current.  Presuming that the voltage and current are always measurable, then there can be no such thing as a breakdown in Ohm's Law.

Simple, I =V/R, in a one shot induced one turn superconductor with a resistance of zero... Ohms law has no application. First there is no resistance and second the equation has no meaning because V/Zero has no meaning. Voltage/Zero = Zero and yet we know as a fact the current would not be zero thus the equation is false in this case.

It is not unlike drag equations in aerodynamics being applied to a craft in space... Uhm there is no drag thus the equations are meaningless. Context matters.

And clearly the "resonant Joule Thief" is dead and the guru Smoky2 has vanished in a puff of smoke.

A resonant joule thief is a no brainier and I have built many. As you may know an LC circuit qualifies a resonant circuit. Thus we can have a battery which powers a joule thief and the output pulse from the JT inductance charges the battery which is powering the JT. The inductor output has coupled to the capacitance of the battery and the rest voltage rises cyclically thus we have a resonant series oscillation which the JT output rides on.
So how would one build this mythical resonant JT you cannot seem to understand?. You simply place a properly sized choke between the battery and the JT which limits the battery input current to the JT but not the periodic voltage rise resting on the capacitance of the battery voltage. I call it a series resonant LC circuit not unlike a delay line... I read about it in a textbook.

AC

[SeaMonkey]

Well said AC!  A sterling example of why your
unique perspective and reasoning skills are
such an important addition to discussion in this
international forum.

Good to see you back!

[MileHigh]

@milehigh

Simple, I =V/R, in a one shot induced one turn superconductor with a resistance of zero... Ohms law has no application. First there is no resistance and second the equation has no meaning because V/Zero has no meaning. Voltage/Zero = Zero and yet we know as a fact the current would not be zero thus the equation is false in this case.

It is not unlike drag equations in aerodynamics being applied to a craft in space... Uhm there is no drag thus the equations are meaningless. Context matters.

I read somewhere that even superconductors have a very very low measurable resistance.  i.e.; Perhaps a superconducting ring will have a L/R time constant of several months, so the current flow will slowly decay.

Secondly, you are talking about a superconducting ring, which looks like an inductor, not a resistor.  Therefore it will behave like an inductor and you can therefore ignore the concept of resistance so ohm's law doesn't apply.

[MileHigh]

A resonant joule thief is a no brainier and I have built many. As you may know an LC circuit qualifies a resonant circuit. Thus we can have a battery which powers a joule thief and the output pulse from the JT inductance charges the battery which is powering the JT. The inductor output has coupled to the capacitance of the battery and the rest voltage rises cyclically thus we have a resonant series oscillation which the JT output rides on.
So how would one build this mythical resonant JT you cannot seem to understand?. You simply place a properly sized choke between the battery and the JT which limits the battery input current to the JT but not the periodic voltage rise resting on the capacitance of the battery voltage. I call it a series resonant LC circuit not unlike a delay line... I read about it in a textbook.

AC

Nope, we are talking about true resonance here, and what you are saying amounts to a word salad unless you can back it up with perhaps a schematic and timing diagram and a proper description relative to those two things.  The output from the JT inductance does not charge the battery.  The "capacitance of the battery" is essentially a meaningless term.

I seriously doubt that you have ever built a "resonant Joule Thief" and simply throwing that description at some kind of circuit that you have built is not applicable.

[allcanadian]

@Milehigh

Nope, we are talking about true resonance here, and what you are saying amounts to a word salad unless you can back it up with perhaps a schematic and timing diagram and a proper description relative to those two things.  The output from the JT inductance does not charge the battery.  The "capacitance of the battery" is essentially a meaningless term.

A battery such as an old 12v 5AH SLA has a fair amount of capacitance the more the plates become sulphated. I have seen a 12v battery with a temporary rest voltage of 50v which can be considered a surface charge. If it isn't capacitance then what is it?.


If we charge a sulphated battery at 13.5v DC that is the temporary charge some of which resides on the plates. If we discharge an inductance into the battery the temporary voltage spikes then slowly drops back to it's rest voltage. Not unlike a capacitor with an internal resistance, in fact exactly like a capacitor with an internal resistance or leakage.


Now what do you think happens when a JT has an input voltage that varies with time... well the output varies with time. It is all very textbook stuff.
http://www.rle.mit.edu/per/ConferencePapers/cpPESC07_p2718_Phi2boost.pdf
You see the JT is a boost converter and most all real EE's have no issue with resonant boost converters... unlike yourself.


AC