if you look closely to the image on the right, you notice the 6th harmonic representing itself as a positive feedback spike. this is not part of the original input signal, but part of the output of the tank.

Smoky2:

Some more comments.

You make reference to resonant radio circuits as in a crystal radio, and I don't see how that applies here.

Modern day "joule thieves" place switching transistors in digital mode with inefficient diodes, successfully destroying the resonant effect.

Yes, but what is implicit in what I say about the JT in oscillation in my previous posting is that there is no "resonant effect" in the way you are suggesting.  There is no special advantageous "effect" that people are "destroying."  I don't know what you mean by "inefficient diodes."

There is still "some effect", because of the natural SRF of the circuit being the dominant factor between the inductor and the tank. but it is disrupted during each cycle, thus a heavier drain on the source than a resonant LRC would or should represent in ideal operation.

Well like I said, the "self-resonant frequency" of the JT circuit in normal operation has zero to do with resonance and what it really is simply an operating frequency based on component values.  It's like for a 555 timer where you select component values.  There is no resonance taking place in a 555 timer when it operates as an astable multivibrator.  So there is no partial "effect."

It is a simple concept, which Americans are indoctrinated to NOT observe.
they teach us these things are bad in circuits, and every way to get RID of this effect.
simply reverse your training to do the opposite.

Sorry but I think it is worth hammering home the point that there is no indoctrination, nothing "bad," no "effect" and no "negative training."  There is no true "alternative way to look at a Joule Thief circuit that 'they' 'don't want you to know.'"  Rather, if you want to learn and master switching circuits then great.  if you want to learn and master basic oscillator circuits using various feedback loops then great.  When you have a mastery of both types of circuits, then can you set up scenarios where switching circuits with built-in amplification will edge towards self-oscillation and understand the whys and the hows?  You bet you can do this if you climb up the learning and experience curve.

So anyway, I wrote this all up to demystify your prose and bring the discussion back to something more rooted in the mundane reality of life.  There is absolutely nothing special about Joule Thief circuits and there is absolutely no "hidden knowledge to uncover" about Joule Thief circuits.  If a Joule Thief circuit can be coaxed into oscillating, then the real thing to do is understand why if you are so inclined.  However, if you are just looking at the net result - how much perceived LED brightness do I get for a given amount of power input, I seriously doubt that any non-standard Joule Thief oscillation mode will outperform a Joule Thief in normal operation mode.

MileHigh

Brad:

Nice.  I have about 40 of those led garden light circuit boards lying around here, those chips they use make a decent JT.
Is that button cell 3 volts or 1.5?  Will it run those down to low voltage as well?

Bill

Hi Bill

Yes,the garden light IC's are extremely small. The battery is a 1.5v battery--that is why you need the small inductor. It will run down to a battery voltage of about .6v.

Brad

Smoky2:

For starters, I sometimes agonize about the concept of an inductor in self-resonance.  In the real world of electronics, that just means that the inductor is crapping out and failing to function as an inductor at the self-resonant frequency.  It's something that an electronics designer wants to avoid, not "take advantage of."  I also agonize about my comment about the inductor acting like a series LC circuit at self-resonance and having minimum AC impedance.  My first intuitive sense is that the model for an inductor is like a parallel LC circuit as shown in the attached diagram.  That means it has maximum impedance at self-resonance.

The irony of this situation, is that you defend your position by quoting said indoctrinated sources....
"electronics designer wants to avoid",.. hmm why is that? do you think? Is it because the results become unpredictable by normal circuit analysis? and "data" as we consider it to be becomes useless or unstable? Thinking of ways to take advantage of this, is exactly what we SHOULD be doing in energy research.

Impedance is a purely electrical function, and at SRF the inductor has a purely capacitive response.
"impedance" through the magnetic portion of the circuit, as you would call it, peaks at a maximum at one half of one half of the waveform (1/4 wave). exactly the opposite occurs when the field collapses, and these two balance each other out perfectly. Hence the term resonance.

Reluctance, on the other hand, which is a purely magnetic function, and at 90-degrees to the electric, this has a value of 0 at SRF, allows the field of the coil to induce a flux in the field of the core material, as a natural response to the resonations within the core itself.
Not as a current-driven forced event.

This is the most important point to get, if nothing else I have stated sinks in.

So I am unsure about this discussion and the answer is ultimately to be found in an actual circuit under test on the bench.  I will just repeat that it is essentially impossible to have a hypothetical discussion like we are having with no circuit, no explanation for how it operates, no schematic, and no timing diagrams.

Now, going back to the basic Joule Thief model, you seem to be implying that if it was operating in some kind of self-resonant mode of the main inductor that forms the transformer core of the device, then it would outperform a comparable Joule Thief operating in its normal mode at a given operating frequency as a switching device.  I have no data at all about that, but my instincts are telling me that that is highly unlikely.

I hereby give your instincts a challenge. Test this for yourself.
Not just by some arbitrary value like "longer run times",. but by measuring the current draw through the battery or source of the circuit, and compare this to the scope image of the coil across the inductor,
then compare this to the output of a secondary coil around the core.

A transistor in linear mode acts like its comparable diode-tube counterpart.
in fact the transistor could be replaced by a triode or something similar.
or dare I mention using something like a self-oscillating quartz resonator used in certain german watches back in the 80s.....

Note that a Joule Thief when operating normally has nothing to do with resonance, which I assume you would agree.  It is just a switching device operating at a given frequency based on component values.

"operating normally" is a vague term when it comes to a device that has been re-engineered in over 100 renditions since Bruce cracked the code on the Steven Marks device....

If you consider a "normally operating joule thief" to be a copy of the one on the Instructables Video
Then yes, I agree it is just a switching device that is most likely oscillating at a frequency incoherent to any SRF of the circuit.

This is because the step-by-step instructions do not include a background of knowledge and education required to understand the true operation of the device. What is given, is a tutorial to build a minimalist version of the oscillator, that is non-self-resonant.

Going back to a Joule Thief operating in some kind of "self-resonant mode" there are lots of issues to ponder about that.  For starters, the transistor can only draw current through the main coil in one direction, but resonance means that current is supposed to flow in two directions, so that is somewhat of a paradox.   If the transistor is operating in its linear region, then that means within the signal there is a DC current drain from the battery through the main coil through the transistor to ground.  So that can't be good for the efficiency of the JT overall because the coil and the transistor are both acting like dumb resistors and producing heat.  Also, in true resonance, there is no magnetic field collapse that outputs energy into a useful load like the LED.  Instead, the magnetic field collapse goes back into the electric field inside the coil.

This is why I said the LED is just an indicator, meant for dummies to know their "JT" is working....
you can throw the LED away, or bypass its drain on the oscillations, by using a capacitor of appropriate value.

The bottom line is this:  I am sure you can mange to hack a JT circuit so that some kind of high frequency oscillation takes place and the LED lights up.  I am not convinced at all that that is related to the self-resonant frequency of the main coil of the JT transformer at all.  I would suspect that any operation at the true self-resonant frequency of the main coil would not really work, the circuit would crap out.  Rather, I suspect that the oscillation is based on some kind of positive feedback between the transistor acting as an amplification device and the JT transformer with some kind of capacitive coupling through a transistor junction being a critical element in the feedback loop.  No matter the case, an investigation into exactly why and how it is oscillating would require some pretty decent electronics smarts and very decent bench skills of which very few on this forum would be in a position to do.  I doubt that I would be able to do it myself unaided but I would be able to follow it and understand it.  It is highly likely that any kind of oscillation mode will light up the JT more efficiently than the JT operating as a simple switching device that energizes an inductor and then discharges it through a LED.

MileHigh

about the circuit crapping out - yes if you take the SRF of most cores and try to run your circuit at that frequency. Better to select a lower resonant node of the cores SRF, which also is an resonant node of the SRF freq. of the LRC of the coil. (and caps if used) - which can be blindly tuned in most cases, by using a variable resistor across the base and carefully observing your oscilloscope.

As for others being able to do this,. yes, read through the JT threads and you see that many are capable of, and do do this.... unfortunately, most of them missed the point, and although they did "tune" into what appeared to be resonant nodes, they usually went right passed them to the nearest peak brightness of the LED, which results in a decay function of the oscillations - more current draw from the source.

This is evident in a few of their scope shots.

sometimes I just feel like im beating my head into the wall... The ones that get it do all sorts of things with this knowledge.. for instance my older brother builds guitar pedals with a JT inside, and never has to worry about replacing the batteries. Most of his house is decked out with LED JT's that have run for years. If he could get one to run his TV hed probably fire the power company.

He's a music major, so he knows all about constructive interference, resonant harmonics, etc...
But even he didn't get it at first. it took me almost 2 years to get him to understand the importance of resonance in this circuit. Once he saw it happen on his scope, it was like a whole world opened up. Now he loves the joule thieves. I go to his house and he has dozens of them, in flashlights, in Altoid Cans, hes taken this further than I ever could. To the point of choosing his own transistors, depending on the waveform he wants, he swears by the old germanium ones. says they work the best.

Smoky2:

In this response I am going to be somewhat minimalist and not quote you, but I will still respond to what you are saying.  The real arbiter of a lot of the points being made is the bench, and I am not in a position to go onto a bench.

I have been watching some debates on YouTube recently about atheism vs. religion and also some debates about evolution vs. creationism.  I see a real tangible parallel with this debate where I take the atheist/scientist side and you take the religious/mystical side.  I submit to you that you have some ideas that are "out there" about electronics stemming from ignorance and/or false beliefs.  Nor do I claim to be an expert on electronics but I can speak reasonably well on the subject.  It's worth it for any person with an active mind to look up the YouTube debates I mentioned.

All that being said, some rebuttals:

- I strongly object to the use of the term "indoctrinated" when it comes to getting a formal education about electronics.

- Electronics designers put a component in a circuit to perform a specific function.  If the component fails to perform the desired function at the required frequency, then you change the component.  Normally there is no chance of finding "advantage" in a situation like this.

- An inductor does not have a "purely capacitive response" at the SRF.  That is simply not the definition of what happens at the SRF.

- You talk about a 1/4 wavelength without saying how the fundamental is defined.  Nor do I think that transmission line and antenna type concepts apply here but I would leave that to experts like Verpies and others to comment on.

- You relate "resonance" to a field collapse and 1/4 wavelengths.  Can you define resonance at the most basic level without even discussing frequency or impedance?  it's important to know what it really means.

- Reluctance does not have a value of 0 at SRF and the whole concept is invalid and makes no sense.

- It makes no sense to measure the current craw of a JT and then compare it with the voltage across a coil.  On face value that makes no sense and the units are not comparable and you would have to add to what you are saying for it to make sense.

- There is no real point in comparing a transistor to a tube in the sense that yes indeed they can perform similar functions but so what?  I fail to see any tangible connection between a transistor operating in linear mode and a quartz timing crystal.

- When I say "operating normally" I am referring to a vanilla JT circuit.

- I would say that the LED is the standard load for a standard JT configuration.  If you replace the LED with a capacitor and presumably some kind of useful load is across the capacitor then you have a primitive buck, boost, or buck/boost converter.

- Using a variable base resistor in a JT circuit will change it's operating parameters and everybody does it.  In a way it's a shame because the real exercise is supposed to be to determine the optimum value for the base resistor.  In a standard JT circuit the base resistor by design is not supposed to be varied.

- I agree that a JT can be tuned but it's not in the way that you are thinking.  The real exercise is to experiment with the JT circuit and see how you can change the frequency and energy of the pulse discharge that lights the LED.  There are no "resonant modes" to find.  Rather, the exercise should be to see what you can do in terms of pulse frequency and energy and initial current and relate that back to perceived brightness and associated power draw.  That would be the real exercise in understanding how the JT works as a switching pulse circuit.

- You are simply quoting anecdotal evidence about your brother's experience so far.  Everybody knows that a JT circuit will suck a battery dry and the same thing will eventually happen with your brother's projects - he hasn't "struck magic."

- Naturally I can't really comment on your brother's circuits, I can just reiterate that a standard JT circuit has nothing to do with resonance at all.

If I could summarize this succinctly I would say that things have to be done one step at a time.  If the JT experimenter could master the original JT first, and truly understood all the issues, then they could look at modifying it and start hacking into it and start getting it to resonate in various ways.  However, then it simply wouldn't be a Joule Thief anymore.

Anyway, you can see there is a divide between what I am saying and what you are saying.  I disagree with your quasi-mystical descriptions of what a Joule Thief is all about and is capable of doing.  There is no point in looking for something esoteric without having a basic and complete understanding of how it works first.  The classic example for that is having a JT light a long string of LEDs in series.  People will play with that without understanding why that happens.  If you truly know how a basic JT works first, then there is no surprise or anything special about a JT lighting a long string of LEDs.

MileHigh

@ Mags

nice presentation

@MH

I can't debate you point over point as you take things out of context...

of course you wouldn't compare only current to only voltage... you compare both to both, over time.

In Physics, the term Resonance is defined as: the reinforcement or prolongation of radiation by reflection from a surface or by the synchronous vibration of a neighboring object. (reverberation)

This definition is very vague and arbitrary and does not describe the details that occur during such an event.
While not every definition of resonance includes the term frequency, or interval of emanation, or any other word used to describe a comparable factor among the components that are said to resonate...
Frequency can be used to compare resonant effects.

The demonstration given above by Mags contains some of those such details.

The most important being that resonant waveforms combine with a particular type of interference.
"Constructive Interference" - this means that along the medium, the two combining waves have a displacement in the same vector. This translates to an increase in Amplitude of the combined waveform, when compared to the original waves. Not all constructive interference is a result of resonance. resonance pertains to a particular relationship between the things "resonating". This can be described as a frequency, or set of frequencies.
You can use other qualities of the resonant waveform to describe it if you wish. I prefer frequencies because it's like an abbreviation, instead of talking about how many times per minute 13 pulses (and their inverse) traveled down the wire....
or some other arbitrary concept used to describe pulses through a circuit.



Similar resonance that occurs with sound, also occurs with all other forms of radiation.
A)Two coherent phase lasers combine with amplitudes that are greater than a simple addition of the two beams.

B)In atomic radiation, close to critical mass, - aside from emissions of high-energy particles causing physical reactions in nearby atoms, there is a radioactive frequency-based effect, that irradiates nearby (nonreactive) atoms, and causes them to resonate at or near the SRF of the reactive atoms. It makes them radioactive. Not by a neutron striking random atoms and increasing their energy levels, but every atom within an irradiated substance increases energy by absorption of the radiating energy into the nuclei. and will radiate this frequency for quite some time. Constructive interference of two radioactive atoms, increases the effective radius of the radiating energy field (with respect to that of a single atom). The energy value for this increase is ^2 (exponential).

C) Heat radiation (in certain discrete conditions) radiates at particular frequencies, or intervals of heat emission.
When two heat waves combine in constructive interference, the amplitude (value of heat) observed at the point of interference, is greater than the addition of the two heat waves.

D) Electricity - when you combine two electrical waveforms in constructive interference, the amplitude of the combined waveform increases as a quantitative factor of the frequency. The "actual" combined waveform is affected by the resistance of the circuit, the speed of propagation, and other factors which make the affect vary slightly from that of sound and light. When these factors are properly taken into account, and invariable constants applied, the resulting complex equation is equivalent to a standard interference analysis as A-c above.

E)Physical Vibration - physical vibrations operate much like a soundwave through a solid mass. Constructive interference of physical vibrations increases in amplitude exactly the same as described above. In addition to the physical waves, there is a component of physical dimension that causes interference feedback. (resonant cavity)

These concepts apply to every branch of physics.
electronics is not excluded. there are REASONS engineers implement counter-resonant tactics to stop this effect from occurring.

MOST of these reasons pertain to circuit stability, and being able to perform the particular function for which the circuit was designed. (you ever watch a radio tower transformer explode from resonant waveforms building up in the antennae?)
This is basically what you were stating, but leads me to ask the question::

For what particular function is your Joule Thief designed?

or did you just copy the instructable?

Resonance is not a mythical belief system, it is a natural occurrence. It is the operating function of the cells that keep you alive, and were it not precisely controlled in your microprocessor, the computer you are using right now would not function. It would simply build up the 2.1Ghz (or whatever) waveform until it shorted out across the silicon.

If you wish to explore this further, the only place I CAN send you is to the bench.

https://wiki.analog.com/university/courses/electronics/comms-lab-isr
This is the very basics of resonance, and pertains mostly to the effects on the coil.
The core used in this experiment assumes the permeability of free space. (air).

Adding a magnetically inductive core, like a ceramic ferrite, can be examined in a similar manner.
Here is someone elses benchwork on this subject.
http://g3rbj.co.uk/wp-content/uploads/2015/08/Self-Resonance-in-Toroidal-Inductors.pdf

Smoky2:

Resonance is an energy storage mechanism.  The critical point being that it is a storage mechanism for energy, it is never a source of energy.

The fundamental description of resonance is that it is a mechanism that stores energy by continuously transforming it back and forth between two complimentary and separate energy storage entities.  In an LC resonator the energy is stored either as voltage across a capacitor or as current flowing through and inductor.  The frequency is determined by the size of the capacitance and the size of the inductance.  That is the basic bare-bones explanation I was looking for.

So for example when a table resonates, the identical process is taking place where energy is stored in two complimentary forms and transfers back and forth between those two forms.

No matter what kind of resonance you are talking about, the same two fundamental properties can be identified and observed.  If you cannot identify and observe them then it is not resonance.

A lot of what you are mentioning is about external signals and how they affect a resonant system where the resonant system has a certain response.  There you are looking at a resonant system acting like a filter to an external stimulus.  Resonance is not really about constructive and destructive interference between two waveforms, that's a whole different story.

So, is a Joule Thief that is operating normally something that demonstrates resonance?  The answer is no.

Resonance is not a mythical belief system, it is a natural occurrence. It is the operating function of the cells that keep you alive, and were it not precisely controlled in your microprocessor, the computer you are using right now would not function. It would simply build up the 2.1Ghz (or whatever) waveform until it shorted out across the silicon.

I don't see anything to do with resonance in living cells.  You can see how easy it is to abuse the term.  You comment about a computer is bizarre. A computer is typically clocked by a crystal oscillator, but that is about as far as it goes.

MileHigh