Joule Thief 101

[MileHigh]

Smoky2:

There is some truth in what you are saying and you are also spinning some tall tales that simply don't make sense.

this is far from a symmetrical balance between the SRF of the coil and the SRF of the core (ideal situation). What is being done here, is changing the capacitance of the coil, with respect to the parasitic capacitance of the core. This, in effect, brings the two waveforms into a resonant node. Meaning, both waveforms have a displacement in the same vector.

Symmetrical balance?  SRF of the core material?  In a standalone core, what would be resonating?  It's a stretch to try to make sense out of that.

Even the most adamant debater against the concept of resonance and constructive interference in electronics circuits, can easily demonstrate the frequency-based efficiency response of biasing the base resistor of a JT.
thus what I have stated above corresponds to experimental results across the board.
Regardless of your perspective of "what is occurring", it still occurs.

Here is the bottom line:  You hack a JT circuit and it starts oscillating.  You measure power in, power to the LED, the apparent brightness, and you look at the waveforms to figure out the mechanism for the oscillation.

There is nothing remarkable going on when you do that.  It's important to state this.  Nobody is saying that you can't do this and nobody "discourages" you from doing this.  You are trying to suggest that something "different" is taking place that "they don't want you to know about" when nothing could be further from the truth.  I will just repeat that when it comes to power draw vs. apparent brightness the chances of outperforming an optimized JT operating normally are very very low.

The hacked JT working as an oscillator will indeed have a "frequency based efficiency response" that can be measured and documented.  Big deal, that is something that would be expected to happen.

You keep reverting back to "standard use of components in electronic circuitry", when the very concept we are talking about is what Electronics as a whole teaches us NOT to do...

Nope, I am going to challenge you on that again.  Electronics as a whole does not teach us to NOT deal with oscillation and resonance.  I am sure you could find full textbooks on oscillator circuits.  Resonance in circuits is a highly studied affair, for both its advantages and for its disadvantages.  You are making a false pitch about electronics and then pitching yourself as the guy that is "teaching you what they don't want to teach you."  The reason I am challenging you is because "resonance" and "what they don't want you to know" are two themes that you see in countless free energy pitches by con men.  The "mystique" of resonance has to be demystified.

What I am describing is not anything "magical". It is the most efficient way to use electricity and magnetic flux.
It might not be the most useful in most applications, but for something like the Joule Thief, TPU, and the LED lightbulbs that are replacing the incandescent,  these concepts can prove to be very useful.

It's easy just to say that but the proof is in the real measurements made on a bench.  With a JT pulsing a LED with just the right frequency so you don't see the LED flickering, and just the right size of transformer so that the right amount of energy is stored per pulse, and the initial current flow lights the LED just the way you want, I think that would be hard to beat.

Not by "generating" energy, but by wasting LESS of it.

No kidding, design engineers have been struggling with this issue seemingly forever.  How long have laptops been around?  Since the late 80s?  Same thing for cell phones.  Engineers have been struggling to increase battery life and make sure that their extremely compact designs with essentially no air flow to remove heat don't spontaneously burn up.  You make it sound like you have "new insight" when in reality the issue of wasting less heat has been a front-and-center issue for design engineers for decades.

and you wonder why I use a term like "indoctrination"

No indoctrination at all.  I think if anything you are making misleading statements about Joule Thieves, resonance, and how engineers deal with resonance, oscillation, and power consumption.  The electronics industry is huge, and the academic world behind it is huge.  It's just a question of recognizing that reality for what it really is.

MileHigh

[sm0ky2]

Smoky2:
SRF of the core material?  In a standalone core, what would be resonating?

MileHigh

Yes, the core material has an SRF.
This information is available from the manufacturer of the core.

(didn't I already say that? I feel like i'm going in circles...)

perhaps, when you're not so high, you should go back through and read it again....

[MileHigh]

Yes, the core material has an SRF.
This information is available from the manufacturer of the core.

(didn't I already say that? I feel like i'm going in circles...)

perhaps, when you're not so high, you should go back through and read it again....

I am not high, but rather trying to make for a rational analysis of some of the things that you are saying so that you and the readers can get a better perspective.

I notice that you yourself can't tell me how a core self-resonates.  You say there was a link and perhaps there is something in the 32 page pdf that you linked to but I am not going to wade through it, I only skimmed through it.  I searched on self-resonance for core material and found next to nothing.  The best thing I came up with was a manufacturer's white paper on ferrite beads showing how they will crap out above a certain frequency and stop working properly.  That might be due to their self-resonant frequency.

http://incompliancemag.com/article/all-ferrite-beads-are-not-created-equal-understanding-the-importance-of-ferrite-bead-material-behavior/

Here is where I think you are tripping yourself up.  Any self resonance in a core material might be at a frequency of say 25 MHz.  That frequency is out of the realm of an operating JT and there is essentially no energy to speak of in those very high frequency ranges to affect the core.  In other words, the core you put in a JT transformer may have a SRF of 25 MHz.  Since there is no frequency content in the signals in the JT in the 25 MHz band then it all means nothing.

It's just like I said that the SRF of an inductor that forms the main coil in a JT normally turns it into a choke, and that frequency might be around 1 MHz.  With respect to a self-resonating ferrite core, for sure that is going to be highly damped because you are flipping magnetic domains at a very high frequency.  So a core does not "ring" at its SRF.

If you hack your JT and it starts to oscillate at say 50 kHz, then the SRF of the main coil of the JT might be 1 MHz and the SRF of the ferrite core might be 25 MHz.  These two things will not affect the hacked JT in an oscillation mode running at 50 kHz.

It's just like I said on another thread that you can't get get any power from the Earth's magnetic field.  Someone else posted and agreed with me but then pointed out if you want to be technical you could in theory pick up a micro-picowatt of power.  It's insignificant and you can simply state that you can't get any power from the Earth's magnetic field.

So if you get a hacked JT to oscillate at 50 kHz, that's all fine and dandy.  However, you can completely ignore the 1 MHz SRF of the coil and the 25 MHz SRF of the core.  Those two tings are totally insignificant and will not affect the operation of the hacked JT in any way whatsoever.

It's important to keep a proper perspective when it comes to electronics.

MileHigh

[Magluvin]

I have a book by John D Lenk   Simplified design of switching power supplies

It has some data charts of some inductors from 10uh to 3.3mh and the SRF of 45mhz to 360khz respectively

Listing under must meet criteria....

Stray capacitance - The inductors self resonant freq must be 5 to 10 times the switching frequency


The book explains SRF briefly...

"All inductors have some distributed capacitance that combines with the inductance to form a resonant circuit. The frequency of this self resonance should be between 5 and 10 times the switching frequency(but not an exact multiple of the switching frequency!). As the inductance value is set by circuit requirements, the SRF is determined by distributed capacitance(a higher capacitance produces a lower SRF).

When SRF is low, the normal linear ramp of the inductor current is preceded by a sudden jump in current when the switching transistor turns on. This results in so called switching losses that lower the regulators overall efficiency. As a result, distributed capacitance should be kept at a minimum so that the SRF will be high and will not seriously affect the inductor current. Distributed capacitance can be lowered when the toroid is wound, either by overlapping the ends of the winding somewhat or by leaving a gap between winding ends(rather than ending the winding at 1 full layer)."

Mags

[sm0ky2]

my only other choice is to keep saying the same thing, in completely different ways.
(looking at it from a different perspective, etc.)
until we merge at a point where both of our perspectives allow for successful communication.

So, here is the scenario, once again. using other parts of the equations, to describe the exact same scenario.

If you graph the frequency response of the inductor (coil w/ ferrite core)
Looking at 3 factors:
1) resistance
2) Impedance
3) Inductive Reactance (This includes both the electric induction and the magnetic reactance counterpart)

There is a point, just before inductance drops off, where the two lines on the graph cross.
(resistance and inductive reactance)
On either side of this crossover point, the characteristics of the inductor completely change.

at frequencies when reactance is greater than resistance - the coil w/ core acts as an inductor.
at frequencies when reactance is less than resistance - the coil w/ core acts as a capacitor. It can be replaced by a capacitor of identical capacitance, and the circuit won't know the difference.

Exactly at the cross-over frequency, Resistance and Inductive Reactance are equivalent. As observable by their magnitude and location on the graph.

At this point, I must state bluntly, that the Impedance of the coil, and the magnetic reluctance-based equivalent of the core material are not the same numerical value. this could potentially be the topic for an entire other discussion, but please understand that there is an impedance mismatch between the electrically inductive coil and the magnetic response at either half of the waveform. This introduces a reflection of a portion of the signal, back to the source.
I could prove this to you, but the device we would be testing would have to be altered in such a way that it is no longer a "joule thief". The transistor and diode do not allow this to pass in the reverse direction. It is blocked through these components. But none of that really matters, because as we already know, the inductor has its' own internal capacitance.
So the reflected portion of the signal still translates, as if this capacitance were an actual capacitor placed in parallel to the transistor+battery portion of the circuit.


This sounds confusing to think about, but that's just how electronic circuits behave. any portion of any circuit can be replace with its' theoretical equivalent circuit, and the circuit (usually) doesn't change at all.
For this reason, we are able to perform transforms, use black-box analysis, and equivalent circuit theory.

The oscillating signal then encounters (or interferes with) this reflected waveform.
The effect can result in a + or - in amplitudes along the voltage or current scale, or both depending upon how the waves interfere. Phase-transitioning can increase or diminish this effect, as observed by the location of the crossover point on the above mentioned graph. When the phase is matched in such a way as to cause constructive interference, system amplitudes increase accordingly. When the phase of the interfering signals is matches in such a way as to cause destructive interference, system amplitudes decrease accordingly.
There are points in the phase transitioning, where the (biased) zero line voltage of the two signals cross in the same location. These signals do not interfere with each other, some examples of this are used in dual-phase or tri-phase applications, such as motors, generators, multi-coil solenoids, and JT's with multiple secondary coil(s) wound on the inductor.
(Multi-phase JT Transformers).
[This non-interfering state does not normally occur in the phase transition between the oscillating signal and the reflected feedback in a JT, This scenario is only presented for knowledge. There is almost always a definable interference between the inductor and its' reflection when used in the Armstrong Oscillator.]

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A Ferrite material, has certain physical mechanical properties, pertaining to the atomic constituents, and their applicable inductance/reluctance, as well as the physical dimensions of the ferrite core. (In the toroid case it is represented as a Diameter, Thickness, and Height).
The SRF of the ferrite core is defined as the resultant frequency derived through a wavelength equation, using these variables.

The physical vibration caused by an oscillating magnetic flux, causes the particles to align opposing the inducing field. When the flux changes, these particles align the other direction.
And there is an associated transitioning function in between, in relation to time.
This defines the "curve" of the magnetic waveform.

When the magnetic waveform induced through the core material and the SRF, as defined, approach equivalence, constructive interference creates, essentially, a standing wave of that wavelength. In an ideal situation (1-3ghz in a standard >1" off the shelf core), the amplitude of this magnetic flux is exponentially greater than that of the two waves. At low frequencies, the effect of this is negligible, and the ideal SRF operation of the inductor results in the same as an addition of the two waves, as a factor of energy over time and the self-defined "second".

There are other frequency-related nodes of resonance, with respect to the SRF of the core material. These are the frequencies generally chosen (actually slightly below this value on purpose) when an electronics engineer choose his inductor for the particular circuit.
why?
because with the fast switching ferrite cores we currently produce, the SRF of the core is considerably higher than the frequencies involved in our circuits.

So we use another frequency or wavelength that meets the 0-line of the magnetic waveform at specified intervals. this is generally a simple division or multiplication of the wavelengths involved. For instance, with a core SRF of 1Ghz, a frequency of 100Mhz would become self-resonant. We would use this core with a wound inductor, at a frequency lower or higher than 100 Mhz. But close to it.... 
We don't use the exact value, because if we did, the impedance mismatch could cause adverse affects in the circuit. But if we did,. what would happen?

Well,. the difference in impedance would act as a capacitance, and a resonant tank would form.
This causes the inductor to physically vibrate on the circuit board, and sometimes even make a ringing noise. Really? the core will make a ringing noise? - yes. This is generally unwanted, and circuits are designed to prevent this. In addition to the noise pollution (and associated losses), other adverse effects can occur at (or very near) the SRF of the core material, or a coherent resonant octave. These can include stray voltage potentials, often exceeding circuit maximums, as well as current spikes that causes heating and can overpower components before or after the inductor. The physical vibrations can also cause the solder connections to break that hold the inductor to the circuit board. In addition to these effects, differences in circuit impedance, combined with the resistive effects of parasitic capacitance, can generate a great deal of heat in the circuit (and associated losses). Making the whole of 'resonance' unappealing to most engineers.

But if we understand why these adverse effects occur, we can design the rest of our circuit so as to avoid these problems. This would mean a complete redesigning of all of our standard circuits.
And for what? I'm not sure that is really necessary. We don't have to (or even want to) use resonant circuits for everything we do. Many applications, simply cannot use this electrical feature in their application. To even try and force this sort of thing into the average circuitboard would undoubtedly destroy something. We are perfectly fine using a value less than the SRF of our components, and calculating the associated losses for doing so. Loss of a picowatt is less expensive than loss of a resistor!!
It is assumed, if not blatantly stated in electronics theory, that our components are not Ideal.
Most of this is a function of resistance / impedance and their circuit-based equivalents.
Here we examine the situation where the "resistance" portion of the circuit is purely in the magnetic domain:

A stand-alone ferrite core, with an applied external magnetic field, oscillating at the cores SRF,
can be set to vibrate on its supports like a high-frequency solenoid. By this we can define the moment of inertia as a function of the ferrite mass with respect to changes in the applied field.
By this we can see that this resonance can occur independent from any electronic circuit.
as the oscillating flux can be electrically or magnetically derived.

The amplitude of these oscillations is a function of the combined magnetic waveforms.
1)The applied flux, and the 2)field changes within the core material.
When you plot their magnitude and vector on a graph, the two resultant waveforms have a phase between them. This pertains to the (constant) frequency of the applied field, and the time derivative of the induced field in the core. (charging time)

At frequencies below the SRF of the ferrite material, the core reaches the maximum value of saturation (with respect to the applied field), faster than the flux is being changed by the applied field. Meaning, the field is not changing as fast as the material "could". When used at these lower than SRF frequencies, the core can reach full saturation, provided enough current.

At frequencies above the SRF (the actual crossover of response time is slightly above the SRF actual value) of the ferrite material, the flux is changing faster than the core can respond.
This means, that at those higher than SRF frequencies, the core does not saturate in time, before the flux changes back in the other direction.

exactly at the SRF of the core material, the standing wave can present itself. Oscillations of the wave are then a pure force derivative between the applied field and the mass and flux of the ferrite. The phase transition between these two waves, affects the total amplitude of the field generated by the flux in the core (or from another viewpoint, the magnitude of the standing wave). This is a direct result of constructive or destructive interference, as seen on the graph.

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How does the SRF of the ferrite relate to the SRF of the coil?

The Coil's SRF is a function of the parasitic capacitance involved, and as such can be changed by a parallel capacitance, or changes in resistances (or changing the effective impedance) in the circuit. We can "tune" the coil's SRF. How and why this occurs is detailed in one of the links I posted above, I wouldn't do it justice by trying to reiterate that here.

When we tune (or phase shift) the SRF of the coil, such that the resonant nodes of both SRFs interfere constructively - the combination of maximum amplitudes of both electric and magnetic flux waveforms, presents itself as the most efficient manner in which to use the coil-wound inductor. In electronics theory, we call this the "Ideal" circuit.
We do not use components this way, because the rest of the circuit is not, or cannot be, does not be, resonant with the SRF of the other components in the circuit.
A modern day example of this is the use of ferrite beads in radio circuits. These are implemented to increase antanea resistance, to prevent current spikes from the receiver signal.
Now, changes in amplitude along a resonant radio frequency signal received by an antenna
are not very large. these are tiny current spikes in this example, but when combined with an amplifier, these can translate into devastating power fluctuations. So, ferrite beads are used to cause Destructive Interference, destroying resonances within the circuit, allowing for a clean signal to be processed by the amplification circuit. "indoctrination" is not necessarily a bad thing. If you are designing circuits that are supposed to perform a specified function, it is easy to see why you DON'T WANT resonances to occur in your circuit. Radio interference can cause problems. You don't hear your song clearly, or a broadcast message is not properly received, or the signal comes through loud and clear then blows out your speaker, or burns up the transistors in the amp.

To sum this all up, most of our Components cannot be operated predictably at their SRF.
This is because (normally) the rest of the circuit is not designed to operate at that frequency.
To design a resonant circuit, Total Circuit Resonance must be observed at all times.
Anything other than, simply results in Destructive Interference in one or more parts of the circuit.
In the words of an old cowboy, you're just shooting yourself in the foot.