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Author Topic: Joule Thief 101  (Read 926750 times)

MileHigh

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Re: Joule Thief 101
« Reply #180 on: February 13, 2016, 05:20:39 AM »
I seriously doubt that a normal Joule Thief can be made to keep the LED on all the time but it can be tried on the bench or in simulation.

The key thing about the Joule Thief transistor is that it snaps ON or it snaps OFF due to positive feedback.

What makes the Joule Thief transistor snap ON is the end of the discharge cycle of the LED.  The potential at the coil-LED terminal drops when the LED discharge is ending.  That drop in potential on the output (right) side of the transformer makes the input (left) side of the of the transformer raise the potential of the base resistor to snap the transistor ON again.

So, it would appear that a Joule Thief can not keep the LED lit all the time because to start a new energizing cycle where you snap the transistor ON, the LED must complete it's discharge cycle and go off such that the energy in the coil is completely depleted first.

You can see how this "winging it" electronics talk can be so fruitless.  No schematics and no timing diagrams and no explanation of the normal operation of the circuit under discussion is the typical backdrop for having a meaningless conversation about electronics while pretending it actually means something.  I have seen discussions of up to 50 postings back and forth that all meant nothing.

On a thread about two or three years ago Poynt got involved in a Joule Thief discussion and some beautiful comprehensive Joule Thief timing diagrams were posted.  I don't recall if they were simulations or scope shots but I think they were supplied by Poynt.  I tried a Google search for Joule Thief timing diagrams but could not find any.

Magluvin

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Re: Joule Thief 101
« Reply #181 on: February 13, 2016, 06:38:56 AM »
I dont want to bring it up further than this, but I wish to reiterate my slight objection to using the circuit I had shown earlier with the led across the transistor.

I went through a search of jt circuits to get a quick view of what seemed most common and some that are variants.

The most popular circuit is the one with the led across the transistor.

The circuit below, which I have labeled as 'wrong'(even though it still works I suppose) seems to take away efficiency by draining the battery when switching on and also draining in series with the discharge into the led. Now below that pic is one that I have labeled 'right' in which I moved the led across the coil instead where it doesnt have the battery draining when the led lights. 

What Im thinking is that the popular circuit 'wrong'(probably the first ever that started it all?) is probably the worst circuit of them to use when we talk efficiency. I would bet that it drains the battery faster than the 'right' circuit. Just being that this is JT 101, that should be discussed a little, maybe.

The 3rd circuit shows a battery being charged as an output and is where I would expect it to be in the circuit. If the battery and the diode were across the transistor and in the 'wrong' circuit, the source battery would be drained as much as the load battery is being charged! ???   Thats not good at all, let alone the source battery has to pump the inductor. Drain and more drain. ::) I want to go the most efficient route here. ;) Never built one but I know how it works. I noticed this issue(to me it is an issue :P ;D ) very quickly just looking at the current paths.

I read once before that a jt is really no more efficient than running the led direct and the only advantage was that it ran on virtually dead batteries. Well if they were testing for efficiency with the 'wrong' circuit, then maybe so. ;)

Had anyone discussed this before possibly?

Mags


Magluvin

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Re: Joule Thief 101
« Reply #182 on: February 13, 2016, 07:24:12 AM »
Looking at the 3rd pic in my post above, it seems the batteries are not correct polarity for the circuit. Picked it from a big list on search. But the output deal is what I wanted to show an example of.

Mags

sm0ky2

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Re: Joule Thief 101
« Reply #183 on: February 13, 2016, 09:18:49 AM »
If I remember correctly (this was a good 7-8 years ago or something...)

The JT circuit sprung from several replication attempts of BruceTPU's self-oscillating circuit.
Which flashed an LED (slowly) for a confirmed 30+days off a capacitor and a resonant tank, which had everyone excited.
Noone was able to replicate what bruce was doing, most of them stated arguments that sound a lot like MH's discussion here.

However, when a battery was added, the circuit performed nicely. Eventually it was found that the batteries don't need to be fully charged. All this was done without the basic operating principals understood.

does the circuit "work" as it is built by a majority of the unknowledged replicators?
I suppose that depends on what you are trying to "do" with it....

If your goal was to light an LED,. then yes I supposed a JT works, no matter how you build it.
There are voltage step-up circuits that will do the same thing much better.

I guess I have the experience of watching the whole thing evolve, from an outside perspective.
I saw the obvious fact that no one was listening to Bruce.
Maybe because they were trained by the industry, perhaps because they could not comprehend the principals.
But at the end of the day, this thing spread around like candy, kids were building them everywhere.

hey LOOK!! this thing can light an LED with a dead battery!!! <<-- this is not even what makes the JT special.....
it is basically a side effect from one particular configuration, that caught on as a fad.

the name "joule thief" was coined some time after the device had been in circulation. The (2 possibly 3) people involved in propagating its' name took the information from the threads and put it in a logical, replicatable form that everyone could easily build. With no knowledge of electronics, signal processing, electrical engineering, physics, magnetics, or any other field that applies to the operation of this circuit. Anyone can copy the design and light an LED with it.

If that is as far as you want to take this technology.. umm,. the door is that way.

To claim that this is not an Armstrong Oscillator, is rather an absurd statement.
Even in its' most simplified form, it still remains such.
The fact that people ignorantly destroy the resonance of the tank, is quite frankly irrelevant.

There was a lot of questions posted recently, I will try to address them here. sorry if I missed one.

@ Mags - on the secondary load,
to put is simply, yes the load affects circuit resonance. Diodes can be used, if resistance can be kept within nominal values. Also, another inductor of greater impedance can prevent destructive feedback.
https://www.youtube.com/watch?v=h9RgjAgSQOg

It is almost a lose-lose situation to try to force the load to be resonant with the coil.
because the primary circuit has a resistance and impedance that differs from that of the ferrite with coil
There is a "mirroring" technique, but it can't really apply to the JT, at least not in the way we use it.

rather the transformer in its' entirety is made to be resonant, and the load is separated by a rectifier circuit,
or appropriate impedance, to prevent destructive feedback from destroying the resonant waveform.

In the above circuit, the number of turns on the secondary coil of the JT, was increased from that of the primary coil, until a resonant node was found.
The second inductor is much larger, with a much greater number of turns on the coil.
The impedance keeps the voltage from fully being achieved in the larger inductor.
Timing of the primary oscillator truncates the amplitude of the waveform, and it presents itself as a lower voltage , higher current signal.
--Note here that the secondary larger ring, is NOT self-resonant with the JT portion of the circuit.
   it oscillates with the resonant freq of the JT, but the ferrite and coil in the second inductor are much different.
The second inductor cannot be made to be self resonant with the coil that is around it.

[When the same large ring is used directly in a JT, the voltages spike to around 90V DC, and almost no current.
some LEDs can pass it through (arc?) , others get damaged.]

-----------------------------------------------------------------------

@ MileHigh

What is the effect of discharging a magnetic inductor (current source) through a coil, when the inductor was magnetically charged, with the lowest possible reluctance?

Does the inductor (current source) then discharge with the most energy possible, because losses are minimized?

Why would you intentionally try NOT to do that?

As for operating JT circuits with voltage sources other than a battery -

You seriously need to do some research. I can name no less than a dozen people on this forum that have posted videos of a JT running from an earth battery. I myself have done this.

https://www.youtube.com/watch?v=xrrFsiMXrvA

There are also many other videos out there using all kinds of voltage sources.

the desk was a woodentop, metal frame desk, upon which sat a lamp, a computer and monitor.
The desk measureably sat at about 43V DC, we assumed because of the electronics sitting on it.
and Yes it powered a JT, because we tried it.

Quote
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

This is a yes, and a no...  more recent JTs use faster reacting LED's. And will in fact flicker rapidly.
Many of the originals used a certain type of Red LED, found in college electronics kits.

These LED's, when powered on, then switched off, take some time to turn off. The light dims gradually.
In most scenarios, using these LEDs in a JT circuit, cut-off time of the LED is longer than half the frequency.
Thus, by the time the LED fully dims, it has already received another pulse and lit back up again.
There is no perceivable "off" condition, by the human eye, or by luminescent monitoring equipment.
What IS perceived, is a dimming of the light. But not a complete off-state.


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sm0ky2

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Re: Joule Thief 101
« Reply #184 on: February 13, 2016, 09:39:57 AM »

What makes the Joule Thief transistor snap ON is the end of the discharge cycle of the LED.  The potential at the coil-LED terminal drops when the LED discharge is ending.  That drop in potential on the output (right) side of the transformer makes the input (left) side of the of the transformer raise the potential of the base resistor to snap the transistor ON again.

So, it would appear that a Joule Thief can not keep the LED lit all the time because to start a new energizing cycle where you snap the transistor ON, the LED must complete it's discharge cycle and go off such that the energy in the coil is completely depleted first.


I'm not sure what you are trying to say here. Makes no sense to me...

a JT can oscillate without the LED present in the circuit.
the LED is only there so you can "see" when the circuit is oscillating.
There are other ways to see this, without using an LED wasting away your energy....

Amplitudes of both voltage AND current increase when the LED is removed.

the "on" - "off" state of the transistor is a function of the inductor/battery circuit, NOT the LED.
you can change the location of the LED, or remove it completely.

The signal at the base from the inductor is what turns the transistor on.
It boosts the voltage from the "dead" battery to above the cut-on voltage of the transistor.
That's what makes the transistor turn on (and the LED light up).
Inductance.
It is a factor of the number of turns on the primary winding.
This is why it is usually such a low number (8-15 turns)

More turns = higher voltage. at some point, you exceed the operating voltage of the transistor.







TinselKoala

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Re: Joule Thief 101
« Reply #185 on: February 13, 2016, 11:09:57 AM »
Yep, all true, pretty much without additional comment necessary.

I've demonstrated my HVJT lighting up 6 NE-2s in series, spiking to over 800 volts, using a AAA battery for input, or even using my wireless power receiver-transmitter system instead of an onboard battery.


Mostly I want to point out that the two circuits using NPN transistors that Mags posted up above are just about equivalent in terms of light intensity and electrical efficiency, as far as I can tell. They work fine using supercaps, but the input voltage must be kept low or the transistor will saturate and stop oscillating, of course. With no LED load they spike to over 26 volts with less than 1 volt input.

Here's a scopeshot of the  Mags "right" circuit (LED across transformer winding rather than across E-C of the transistor). I made a 6-pad version and used a MPSA18 transistor and a 150 ohm base resistor to keep it consistent with my "standard" 6-pad JT, and I used 2 Max Lumileds in series as the load. Both circuits give an illumination of about 11.5 lux at my standard 43 cm distance in my lightbox.

I don't know what to say about the PNP circuit up above, I've never tried it myself. I have made some PNP JTs... in fact the standard circuit will generally work with a PNP transistor if you reverse E and C connection and battery polarity. (IIRC... I don't have one set up at the moment.)

TinselKoala

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Re: Joule Thief 101
« Reply #186 on: February 13, 2016, 01:42:57 PM »
OK... to do a more valid comparison of the two circuits (Mags's "right" with LED across the coil, and the Standard "wrong" with LED across E-C of transistor) I wound another toroid of 36+36 turns (arbitrarily chosen) and breadboarded the two circuits with the same components each time, to eliminate variations due to component differences. I used a 1000 ohm gate resistor, an MPSA18 transistor, two Max LumiLEDs in series as load, and the toroid, all same components in both cases. I used my lightbox with Extech LT300 lightmeter to check the brightness of the LED load at 18 inches from LEDs to sensor. It's simple to rewire the breadboard from one configuration to the other, just have to change one wire. I used the same depleted AG13  alkaline button cell, which measures 1.27 volts open-circuit (after running the tests).

So, the scopeshots below show the two circuits.
#128 is the "Mags right" circuit, and it produced a reading of 8.5 Lux on the lightmeter.
#129 is the "Standard wrong" circuit, and it produced a reading of 9.8 Lux on the lightmeter.

Later on I'll do an electrical efficiency test by measuring the average input power to the circuits and compare that to the brightness, so I'll get values in Lux per Watt for the two circuits.

MileHigh

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Re: Joule Thief 101
« Reply #187 on: February 13, 2016, 09:58:59 PM »
Smoky2:

Quote
To claim that this is not an Armstrong Oscillator, is rather an absurd statement.
Even in its' most simplified form, it still remains such.
The fact that people ignorantly destroy the resonance of the tank, is quite frankly irrelevant.

It is clearly not an Armstrong oscillator and there is no resonant tank.  There is nothing absurd about my statement at all. You simply have to look at a Joule Thief schematic and compare it to the schematics of an Armstrong oscillator.  See attached.

So if you want to make that claim and have it taken seriously then you have to go beyond just posting text.  Right now you are the one making the absurd statement.

Quote
What is the effect of discharging a magnetic inductor (current source) through a coil, when the inductor was magnetically charged, with the lowest possible reluctance?

Does the inductor (current source) then discharge with the most energy possible, because losses are minimized?

Why would you intentionally try NOT to do that?

If I understand your question properly, and that's sometimes difficult because you are sparing with your words, when one inductor discharges into another inductor (presumably with no current flowing through it) then you get a near-instantaneous spike of voltage from the first inductor inducing the second inductor to get current flowing though it.  In a very short amount of time both inductors have the same current flowing through them.  The original current flowing in the first inductor takes a step down such that the energy is conserved.

I don't know why you say, "Why would you intentionally try NOT to do that?" because there is seeming no discernible context to whatever point you are trying to get across.

Quote
You seriously need to do some research. I can name no less than a dozen people on this forum that have posted videos of a JT running from an earth battery.

The problem is that you did not say "earth battery" you said "earth."  Of course a Joule Thief can run from an earth battery which in reality is just current due to the slow corrosion of a metal like magnesium.

Quote
the desk was a woodentop, metal frame desk, upon which sat a lamp, a computer and monitor.
The desk measureably sat at about 43V DC, we assumed because of the electronics sitting on it.
and Yes it powered a JT, because we tried it.

One more time, it's the same issue.  All that you said was "metal frame desk" and you said nothing beyond that.  If you made serious measurements on the "output" of the desk you would quote more than just "43V DC" which is almost meaningless.

Quote
These LED's, when powered on, then switched off, take some time to turn off. The light dims gradually.

I'd be more than happy to look at an LED data sheet showing that if you can link to one.

MileHigh

sm0ky2

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Re: Joule Thief 101
« Reply #188 on: February 13, 2016, 10:18:02 PM »
@ TK - I love the clothespin battery holder :)


@ MH - in your comparative analysis of the two circuits, did you notice the functional difference between the two diagrams?

essentially, they operate the same, minus one important factor.

the R-C component of the tank circuit vs the L of the coil are set to resonate with each other.
This, not taken into consideration in the JT equivalent circuit, reduces performance.

The same could be said about the Armstrong circuit, if one chose to change the value of R or C.

MileHigh

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Re: Joule Thief 101
« Reply #189 on: February 13, 2016, 10:36:51 PM »
Smoky2:

Quote
a JT can oscillate without the LED present in the circuit.
the LED is only there so you can "see" when the circuit is oscillating.
There are other ways to see this, without using an LED wasting away your energy....

Amplitudes of both voltage AND current increase when the LED is removed.

In a regular Joule Thief if you remove the LED it will presumably still operate like you state.  The inductor would have no choice but to discharge through the transistor.  The average power is low so presumably it would not fry the transistor junctions.

The voltage output from the coil will spike to a quite high voltage, it all depends on the speed that the transistor switches off.  However, I have "caught" you here with respect to the discharge current.  The current will NOT increase.  Are you sure that you fully understand the complete dynamics of an inductor?

Quote
the "on" - "off" state of the transistor is a function of the inductor/battery circuit, NOT the LED.
you can change the location of the LED, or remove it completely.

I strongly suggest that you go back and watch the clip about the operation of a Joule Thief that I linked to the other day to review the positive-feedback "snapping" mechanism that switches the transistor ON and OFF and governs the operating frequency of the device.  It is also related to the rate of change of current flow through the main coil which is indeed related to the characteristics of the inductor and battery combination.

Quote
The signal at the base from the inductor is what turns the transistor on.
It boosts the voltage from the "dead" battery to above the cut-on voltage of the transistor.
That's what makes the transistor turn on (and the LED light up).
Inductance.
It is a factor of the number of turns on the primary winding.
This is why it is usually such a low number (8-15 turns)

More turns = higher voltage. at some point, you exceed the operating voltage of the transistor.

I agree that you can experiment with the number of turns in the coil that connects to the base resistor.  If you do that then you may want to change the value of the base resistor.  In the context of what you are stating, a transistor does not have an "operating voltage" it has an operating current.

MileHigh

MileHigh

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Re: Joule Thief 101
« Reply #190 on: February 13, 2016, 10:52:52 PM »
@ MH - in your comparative analysis of the two circuits, did you notice the functional difference between the two diagrams?

essentially, they operate the same, minus one important factor.

the R-C component of the tank circuit vs the L of the coil are set to resonate with each other.
This, not taken into consideration in the JT equivalent circuit, reduces performance.

The same could be said about the Armstrong circuit, if one chose to change the value of R or C.

I really don't know what you are saying here when you refer to the resistance in the Armstrong oscillator tank circuit.  For sure it is there but it is not relevant to the powered oscillation of the LC tank.

In a Joule Thief, the operating frequency is dependent on L/R type time constants, one L/R time constant for the energizing of the coil, and another L/R-type time constant for the discharge of the inductor energy through the LED.

Now, seriously, how can you equate the resonant frequency of an Armstrong oscillator based on an LC resonant tank and the operating frequency of a Joule Thief based on a first L/R time constant for the energizing of the main coil and a second L/R-type time constant for the discharging of the coil through the LED?

Armstrong oscillator:  operating frequency determined by LC resonant tank.

Joule Thief:  operating frequency determined by (1/(L/R time constant#1 + L/R time constant#2))

Can you see how completely different these two methods are for determining the operating frequency are and how a Joule Thief's operating frequency has absolutely nothing to do with resonance?

MileHigh

sm0ky2

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Re: Joule Thief 101
« Reply #191 on: February 13, 2016, 11:13:42 PM »
I really don't know what you are saying here when you refer to the resistance in the Armstrong oscillator tank circuit.  For sure it is there but it is not relevant to the powered oscillation of the LC tank.

In a Joule Thief, the operating frequency is dependent on L/R type time constants, one L/R time constant for the energizing of the coil, and another L/R-type time constant for the discharge of the inductor energy through the LED.

Now, seriously, how can you equate the resonant frequency of an Armstrong oscillator based on an LC resonant tank and the operating frequency of a Joule Thief based on a first L/R time constant for the energizing of the main coil and a second L/R-type time constant for the discharging of the coil through the LED?

Armstrong oscillator:  operating frequency determined by LC resonant tank.

Joule Thief:  operating frequency determined by (1/(L/R time constant#1 + L/R time constant#2))

Can you see how completely different these two methods are for determining the operating frequency are and how a Joule Thief's operating frequency has absolutely nothing to do with resonance?

MileHigh

you are basically peeling an apple, taking the seeds out and proclaiming, see, this is not an apple at all....

the Resistance/Impedance of the Armstrong circuit is equally important as the Capacitance and Inductance.
In fact, all 3 must be maintained in perfect balance for the circuit to be resonant at that frequency.

This quality makes the Armstrong Oscillator an RLC circuit, Not simply an LC tank.
Though, under certain analysis, the two can behave similarly.

[I would go even further by stating that an LC tank is technically defined also as an RLC.
because of our wires containing some resistance value, but its effect on resonance frequencies can be negligible]

the Joule Thief, is also an RLC circuit, and its' type is classified as an Armstrong Oscillator.
this is a technical definition written in the stone of electronics theory.
Many RLC circuits exist, and most of them are named according to their Inventor, or a particular aspect of their operation.
When we classify the Joule Thief, this is the category it falls under.
all circuits that fall into this category are considered to be Armstrong Oscillators.


sm0ky2

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Re: Joule Thief 101
« Reply #192 on: February 13, 2016, 11:19:40 PM »
I have done, what I think is (currently) my best attempt to bring this knowledge into the public realm, as it pertains to the JT circuit.

To understand more, from perhaps a more technical aspect than I myself can present.
I would direct you to the works of Edwin Armstrong - who is considered by some to be the GodFather of radio.

http://users.erols.com/oldradio/


sm0ky2

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Re: Joule Thief 101
« Reply #193 on: February 13, 2016, 11:57:02 PM »
Smoky2:

In a regular Joule Thief if you remove the LED it will presumably still operate like you state.  The inductor would have no choice but to discharge through the transistor.  The average power is low so presumably it would not fry the transistor junctions.
You make some big assumptions here, but outside of resonant frequencies, yes your electronics should be safe, given the parameters of the system to be within tolerance.


Quote
The voltage output from the coil will spike to a quite high voltage, it all depends on the speed that the transistor switches off.
This "speed" you speak of,. this wouldn't be related to "frequency" would it?
More specifically, the frequency-dependent curve of the transistor switching function?

Quote
However, I have "caught" you here with respect to the discharge current.  The current will NOT increase.  Are you sure that you fully understand the complete dynamics of an inductor?
Allow me to clarify, by "increase" upon removal of the LED, it can instead be stated that:
by including an LED, there is a drop in current through the parallel paths, and an associated voltage drop across the diode.
This is important to consider, when analyzing the feedback signal.
It represents a higher impedance, as well as a lower voltage.
Impedance differs from a purely resistance perspective,
because changes in amplitude over time as well as phase come into play.
Note that it does not matter if this impedance is included in series or parallel.
Though its' physical location around the loop does affect certain parameters,
 as shown in TK's demonstration above. <- while this makes for great conversation,
 I feel that is above the technical level of a basic "101" crash course.

Quote
I strongly suggest that you go back and watch the clip about the operation of a Joule Thief that I linked to the other day to review the positive-feedback "snapping" mechanism that switches the transistor ON and OFF and governs the operating frequency of the device.  It is also related to the rate of change of current flow through the main coil which is indeed related to the characteristics of the inductor and battery combination.

I do not particularly agree with the assumptions made by that analysis.
While these factors are related, as I have described in previous posts,
phase angle between the signals must be properly considered to discuss what is being shown.

Quote
I agree that you can experiment with the number of turns in the coil that connects to the base resistor.  If you do that then you may want to change the value of the base resistor.  In the context of what you are stating, a transistor does not have an "operating voltage" it has an operating current.

MileHigh

Hmm,.. I've run into this before.  where I come from we use terms like Cut-in/Cut-out, or Cut-On/Cut-Off.
What this refers to is:
the voltage threshold that represents the transition stage between:
the Cut-Off and Active regions of the transistor. Below this voltage, the semiconductor does not allow current to pass.
Above this voltage current can travel.
This function is controlled in part by the base voltage (bias).

The transistor in the Joule thief transitions between Cut-off and forward active operation modes.
(up to the point of saturation) at which point the diode becomes the primary conductor until voltage potential drops below
the cut-off of the LED. at which point it begins to dissipate its' capacitance as light. (discharge)
Saturation only generally occurs in a JT when the LED(s) have a high internal capacitance (long discharge time).
This allows for a unique scenario when the voltage drop across the diode makes the emitter voltage appear lower than the base.

Otherwise, the transistor remains in one of these two states.
The actual timing diagram of the switching function, can display a wide range of characteristics.
Outside of linear mode, and/or resonant operation - this function appears as a sharp spike at cut-on, and a gradual decrease at cut-off. (removing the LED changes the shape of these spikes).
When operated in linear mode, at resonance, it is a pure sine-wave function, with varying amplitudes.

MileHigh

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Re: Joule Thief 101
« Reply #194 on: February 14, 2016, 12:01:44 AM »
you are basically peeling an apple, taking the seeds out and proclaiming, see, this is not an apple at all....

the Resistance/Impedance of the Armstrong circuit is equally important as the Capacitance and Inductance.
In fact, all 3 must be maintained in perfect balance for the circuit to be resonant at that frequency.

This quality makes the Armstrong Oscillator an RLC circuit, Not simply an LC tank.
Though, under certain analysis, the two can behave similarly.

[I would go even further by stating that an LC tank is technically defined also as an RLC.
because of our wires containing some resistance value, but its effect on resonance frequencies can be negligible]

the Joule Thief, is also an RLC circuit, and its' type is classified as an Armstrong Oscillator.
this is a technical definition written in the stone of electronics theory.
Many RLC circuits exist, and most of them are named according to their Inventor, or a particular aspect of their operation.
When we classify the Joule Thief, this is the category it falls under.
all circuits that fall into this category are considered to be Armstrong Oscillators.

No in fact the resistance is not that critical in the RLC resonator because it is an active circuit where an external power source keeps the resonator resonating regardless of the inherent resistance in the resonating components.  There is no special balance with regards to the resistance in what is essentially an LC resonator.

Th Joule Thief is not an RLC circuit as I have clearly shown.  It is an active circuit that charges and then discharges a coil.  It's the charging cycle and the discharging cycle that determine the operating frequency, and there is no RLC resonator in sight.  Instead there are two L/R-type time constants that factor in to determine the operating frequency of the Joule Thief in its standard normal operating mode.

You can try to ignore what I am saying, but facts are facts.  Anybody that is interested in electronics would want to study and learn about both pulse circuits and resonating circuits and the associated need to be able to recognize and make a distinction between pulse circuits and resonating circuits.

Note that I am not talking about a hacked Joule Thief circuit here, just an ordinary plain vanilla Joule Thief that is a basic pulse circuit that switches a transistor on and off.  It's a distant cousin of a 555 timer circuit configured as a free running astable multibrator.  Likewise, a 555 running as an astable multivibrator has nothing to do with resonance.  Its operating frequency is determined by RC time constants whereas for the Joule Thief its operating frequency is determined by L/R time constants.

Like I said, you have a "fan club" and anyone interested in Joule Thieves should build a standard Joule Thief first and understand how it operates and probe it with their scope and observe the positive feedback mechanisms in operation.  Then if they want to hack into it and try to make it resonate then more power to them.  The critical point being that if they are claiming resonance then they need to identify the L and C components that are exchanging energy back and forth and show that in action.

MileHigh