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Author Topic: Joule Thief 101  (Read 926703 times)

tinman

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Re: Joule Thief 101
« Reply #195 on: February 14, 2016, 02:20:46 AM »
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

Quote
Th Joule Thief is not an RLC circuit as I have clearly shown.

How did you ever come up with that MH ?.
The JT is most certainly an RLC circuit.


Brad

Magluvin

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Re: Joule Thief 101
« Reply #196 on: February 14, 2016, 02:30:24 AM »
Thanks for taking the time to do those tests TK.

Mags

MileHigh

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Re: Joule Thief 101
« Reply #197 on: February 14, 2016, 02:56:23 AM »
How did you ever come up with that MH ?.
The JT is most certainly an RLC circuit.

Brad

Really?  Take a look at the attached diagram.  This is an intentionally simplified explanation showing the two principal processes that determine the operating frequency of the Joule Thief that ignores the battery voltage and the positive feedback transistor switching process.

There used to be a good explanation on the operating frequency of a Joule Thief that went into quite a bit of detail on Wikipedia but apparently it was disputed because it has since been removed.  Here is a link that discusses the inductance being a prime factor with some information from the older version of the now-modified Wikipedia page:

http://www.elperfecto.com/2011/01/22/toroidal-inductors-number-of-turns-affects-joule-thief/

Feel free to make your case for a Joule Thief being an RLC circuit.

MileHigh

Magluvin

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Re: Joule Thief 101
« Reply #198 on: February 14, 2016, 03:12:33 AM »
Just made a quick sim of the right and wrong circuits running simultaneously. The circuits do work. The left is what I had labeled as 'wrong' and the circuit on the right is, well, 'right' ;D

The scope shots are source(1.5v batt) pk power traces to the left, top is 'wrong' and bottom is 'right'. And the traces on the right are the leds, top 'wrong' bottom is 'right'.    The power traces are peaks, not average power. So we will leave it up to TK to determine which circuit has the advantage of pulling less from the source. He has shown a higher lux from the leds with the 'wrong' circuit so far. Im not sure if that is a noticeable difference in brightness to the eye.

The 'right' circuit has a higher running freq.   

If you slow down the sim control slider, the 'wrong' circuit it seems the transistor never really turns off and always draining the source, along with the led draining the source when it is on. And the 'right' circuit the transistor does turn off and the led does not drain the source when on.

Here is the code for the sim. For some odd reason the codes dont always provide the scopes as what shows when the code is exported. I retried the code and it did this time.


$ 1 5.0E-6 0.625470095193633 50 5.0 43
t 416 400 496 400 0 1 -1.403784455736806 0.7049612942489206 100.0
w 496 416 496 448 0
w 496 448 336 448 0
169 416 240 496 240 0 1.0E-4 1.0 -0.001746210276144522 1.2763726782599143 1.2763726782599143
w 496 240 496 208 0
w 496 208 416 208 0
s 336 208 416 208 0 0 false
v 336 448 336 208 0 0 40.0 1.5 0.0 0.0 0.5
r 384 304 384 400 0 100.0
w 496 384 496 304 0
w 496 304 560 304 0
w 496 448 560 448 0
162 560 304 560 448 1 2.1024259 1.0 0.0 0.0
w 416 208 384 240 0
w 384 240 416 304 0
w 416 240 384 304 0
w 384 400 416 400 0
w 784 400 816 400 0
w 816 240 784 304 0
w 784 240 816 304 0
w 816 208 784 240 0
w 896 384 896 304 0
r 784 304 784 400 0 100.0
v 736 448 736 208 0 0 40.0 1.5 0.0 0.0 0.5
s 736 208 816 208 0 0 false
w 896 208 816 208 0
w 896 240 896 208 0
169 816 240 896 240 0 1.0E-4 1.0 5.1958437552457326E-14 0.31968522644013664 0.3196852264401375
w 896 448 736 448 0
w 896 416 896 448 0
t 816 400 896 400 0 1 -4.049226601125407 -0.5211382639894485 100.0
w 896 304 944 304 0
w 896 240 944 240 0
162 944 304 944 240 1 2.1024259 1.0 0.0 0.0
o 7 1 1 291 4.676805239458889 9.765625E-55 0 -1
o 23 1 1 291 4.676805239458889 9.765625E-55 0 -1
o 12 1 1 35 5.0 9.765625E-5 1 -1
o 33 1 1 35 5.0 9.765625E-5 1 -1


Mags

Magluvin

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Re: Joule Thief 101
« Reply #199 on: February 14, 2016, 03:52:34 AM »
It seems the code I posted has the resistor at 100ohm.  Change to 500ohm to show what I posted in the pic.. 100ohm here tends to run the circuit in the greater than 1 watt range. Trying to stay some what in bounds.  The transformer is 1:1 100uh.   Didnt play with transistor or led settings.

Mags

sm0ky2

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Re: Joule Thief 101
« Reply #200 on: February 14, 2016, 09:30:17 AM »
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.

MileHigh

Bullshit.

When you alter the resistance in a RLC circuit, you CHANGE the resonant frequency.
This is a self-defined term.
Resistance is an important factor in the equations.


[go ahead and do a search on my name, and see how many times I declare bullshit on someone.......]



MileHigh

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Re: Joule Thief 101
« Reply #201 on: February 14, 2016, 10:09:37 AM »
Bullshit.

When you alter the resistance in a RLC circuit, you CHANGE the resonant frequency.
This is a self-defined term.
Resistance is an important factor in the equations.

The most complete response I can give you to that is yes and no.

Yes in the sense that an electronics expert, the late MarkE, stated that the resistance can affect the self-resonant frequency and I was quite surprised.  I don't remember the details but he clearly stated that the value of the resistance can marginally affect the self-resonant frequency and I am quite certain that this effect came into play for larger resistances.

No in the sense that we are talking about a LC circuit where the resistance is typically very low and will not have any real effect on the self-resonant frequency as defined by "omega = 1/sqrt(LC)."  That is a very familiar formula that most people are aware of.

Here is the Google search link for, "resonance of an rlc circuit:"

https://www.google.ca/?gws_rd=ssl#q=resonance+of+an+rlc+circuit

In the first six links you will see the resonance frequency defined for both serial and parallel RLC circuits as "omega = 1/sqrt(LC)" even when they clearly show resistances in the RLC circuits being discussed.  In other words they are ignoring the value of the resistance because in the majority of cases it can be ignored.

So, we are coming back to reality:  For nearly all practical intents and purposes, the resonant frequency of an RLC circuit is a function of the inductance and capacitance only.  When the only resistances in the circuit are associated with the inductor and capacitor themselves and they are quite low, then it is only a function of the inductance and capacitance.  That is a reasonable answer that covers all the bases.

Quote
Resistance is an important factor in the equations.

Really?  Then the floor is yours.  Please go ahead and explain exactly what you mean in detail.  What are the equations?

MileHigh

tinman

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Re: Joule Thief 101
« Reply #202 on: February 14, 2016, 01:00:00 PM »
Really?  Take a look at the attached diagram.  This is an intentionally simplified explanation showing the two principal processes that determine the operating frequency of the Joule Thief that ignores the battery voltage and the positive feedback transistor switching process.

There used to be a good explanation on the operating frequency of a Joule Thief that went into quite a bit of detail on Wikipedia but apparently it was disputed because it has since been removed.  Here is a link that discusses the inductance being a prime factor with some information from the older version of the now-modified Wikipedia page:

http://www.elperfecto.com/2011/01/22/toroidal-inductors-number-of-turns-affects-joule-thief/

Feel free to make your case for a Joule Thief being an RLC circuit.

MileHigh

As soon as you have two conducting wires wound around a core next to each other,then you also have a C value. This is more so pronounced due to the fact that the current through these two conducting wires flows in opposite directions at the same time with the JT circuit. There is also the fact that the transistor it self has Capacitance,and this C value alone also plays a factor in the operating frequency of the circuit. I have shown you before with my cool joule circuit that the Miller effect alone can send the circuit into oscillation without any inductive coupling at all between the two coil's. So to say that the JT has no C value is wrong-very wrong.


Brad

tinman

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Re: Joule Thief 101
« Reply #203 on: February 14, 2016, 01:26:01 PM »
The most complete response I can give you to that is yes and no.



No in the sense that we are talking about a LC circuit where the resistance is typically very low and will not have any real effect on the self-resonant frequency as defined by "omega = 1/sqrt(LC)."  That is a very familiar formula that most people are aware of.

Here is the Google search link for, "resonance of an rlc circuit:"

https://www.google.ca/?gws_rd=ssl#q=resonance+of+an+rlc+circuit

In the first six links you will see the resonance frequency defined for both serial and parallel RLC circuits as "omega = 1/sqrt(LC)" even when they clearly show resistances in the RLC circuits being discussed.  In other words they are ignoring the value of the resistance because in the majority of cases it can be ignored.

So, we are coming back to reality:  For nearly all practical intents and purposes, the resonant frequency of an RLC circuit is a function of the inductance and capacitance only.  When the only resistances in the circuit are associated with the inductor and capacitor themselves and they are quite low, then it is only a function of the inductance and capacitance.  That is a reasonable answer that covers all the bases.

Really?  Then the floor is yours.  Please go ahead and explain exactly what you mean in detail.  What are the equations?

MileHigh

Quote
Yes in the sense that an electronics expert, the late MarkE, stated that the resistance can affect the self-resonant frequency and I was quite surprised.  I don't remember the details but he clearly stated that the value of the resistance can marginally affect the self-resonant frequency and I am quite certain that this effect came into play for larger resistances.

MarkE was indeed a great man,but even he had room to learn. Im sure you remember the thread MH (i cant),where i presented my cool joule circuit,and told MarkE that it operated due to the miller capacitance effect. At first he refused to believe that to be true, but then later on came back and confirmed that it was indeed the miller effect that was causing the circuit to oscillate.

There are those that dwell on these forum's that dont have much to say,but there knowledge far exceeds that of those here that often make a stand on what they believe to be true. Vortex1 is one of those extremely well versed in EE,and it's due to experience/bench time. He is also the one that worked out how my cool joule circuit was operating--i had no idea as to how or why it was working at the time,but now-because of Vortex1,i know exactly how it works.

The cool joule circuit operation was found quite by accident. I had one coil on top of the other,and as we would expect,the circuit ran quit fine. But when i went to reach for the soldering iron,i knocked the top coil of the bottom one-but the circuit still kept on oscillating :o. So i moved the top coil (base/emitter-trigger coil) further away from the drive coil,and still it kept oscillating. After a distance of over 1 meter between the two coils,we can eliminate the fact that any inductive coupling between the two coils was taking place,and so i presented this mystery circuit as the cool joule circuit,as i thought it was pretty cool that it operated without any inductive coupling between the two coils.

Anyway,i think you would be wise to listen to what Smokey has to say,as the JT definitely is an RLC circuit.


Brad

MileHigh

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Re: Joule Thief 101
« Reply #204 on: February 14, 2016, 02:32:46 PM »
As soon as you have two conducting wires wound around a core next to each other,then you also have a C value. This is more so pronounced due to the fact that the current through these two conducting wires flows in opposite directions at the same time with the JT circuit. There is also the fact that the transistor it self has Capacitance,and this C value alone also plays a factor in the operating frequency of the circuit. I have shown you before with my cool joule circuit that the Miller effect alone can send the circuit into oscillation without any inductive coupling at all between the two coil's. So to say that the JT has no C value is wrong-very wrong.

Brad

You are not making a case for a Joule Thief being an RLC circuit.  What that is supposed to mean is that the operating frequency is based on an LC resonant tank frequency and you can show how a Joule Thief is an actual RLC circuit.

What you are saying is that there is stray capacitance in the circuit.  Likewise there is stray inductance in the circuit.  In fact, for any circuit there is stray capacitance and stray inductance.  Sometimes it is significant, but most of the time it is insignificant at the normal operating frequency of the circuit.  Part of learning about electronics is to recognize when something is significant or not.

So I will ask you again, is a Joule Thief an RLC circuit or not?  If you say it is and the operating frequency is determined by an LC resonator, then please show the circuit, show where the resonator is, and describe now it operates.  Your discussion about stray capacitance above does not back up your claim.

MileHigh

MileHigh

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Re: Joule Thief 101
« Reply #205 on: February 14, 2016, 02:47:40 PM »
Brad:

Quote
There are those that dwell on these forum's that dont have much to say,but there knowledge far exceeds that of those here that often make a stand on what they believe to be true. Vortex1 is one of those extremely well versed in EE,and it's due to experience/bench time.

It's not a question of me "believing it to be true," I know what I am saying is true.  Rather, you are "believing it to be an RLC circuit."  Now if you were wise, you would actually look at what I stated about the Joule Thief and how it operates.  I did that over several postings and you are seemingly ignoring that and made no attempt to rebut it.  I linked to a clip that describes exactly how a Joule Thief operates with a full five minute description.  You are seemingly ignoring that also and making no attempt to rebut that.

If you are going to simply ignore what I said then it's willful ignorance on your part and you don't advance.  Look at what I said, look at what Smoky2 said, look at what you yourself said, and go online and do some of your own research.  Don't just almost blindly say, "Oh, a Joule Thief is an RLC circuit because there is some stray capacitance between the windings" because that is dead wrong.  It's nothing more than an incorrect "drive by" evaluation of a Joule Thief circuit.

MileHigh

tinman

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Re: Joule Thief 101
« Reply #206 on: February 14, 2016, 02:55:01 PM »
Brad:

It's not a question of me "believing it to be true," I know what I am saying is true.  Rather, you are "believing it to be an RLC circuit."  Now if you were wise, you would actually look at what I stated about the Joule Thief and how it operates.  I did that over several postings and you are seemingly ignoring that and made no attempt to rebut it.  I linked to a clip that describes exactly how a Joule Thief operates with a full five minute description.  You are seemingly ignoring that also and making no attempt to rebut that.

If you are going to simply ignore what I said then it's willful ignorance on your part and you don't advance.  Look at what I said, look at what Smoky2 said, look at what you yourself said, and go online and do some of your own research.  Don't just almost blindly say, "Oh, a Joule Thief is an RLC circuit because there is some stray capacitance between the windings" because that is dead wrong.  It's nothing more than an incorrect "drive by" evaluation of a Joule Thief circuit.

MileHigh

The JT works quit fine without inductive coupling between the two winding's,and the reason it dose that is due to the C value of the transistor. When operating at low voltages as the JT dose,and the frequencies involved,the transistors own capacitance plays a vital roll. We know this capacitance exist,so i am at a loss as to how you can say it dose not ???. As it dose exist,and is part of the circuit,then the circuit !is! an RLC circuit.


Brad.

MileHigh

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Re: Joule Thief 101
« Reply #207 on: February 14, 2016, 03:09:11 PM »
The JT works quit fine without inductive coupling between the two winding's,and the reason it dose that is due to the C value of the transistor. When operating at low voltages as the JT dose,and the frequencies involved,the transistors own capacitance plays a vital roll. We know this capacitance exist,so i am at a loss as to how you can say it dose not ??? . As it dose exist,and is part of the circuit,then the circuit !is! an RLC circuit.

Brad.

Nope, you aren't going to actually show how a Joule Thief is an RLC circuit and show how it operates as an RLC circuit because you can't.  You can't sketch out the circuit or sketch out timing diagrams to back up what you are claiming.  What you are doing is making up a word salad.

Also, the Joule Thief will not work as a Joule Thief, if it woks at all, without the inductive coupling between the two windings.  Saying it works because of "the C value of the transistor" is just more word salad.

The fundamental timing and operation of a Joule Thief is based on L/R time constants and there is no resonance at play at all - the Joule Thief timing and operation is governed by the interaction between inductance and resistance and not capacitance.

MileHigh

sm0ky2

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Re: Joule Thief 101
« Reply #208 on: February 14, 2016, 08:41:56 PM »
we can just "ignore" this 100k Ohm resistor


pay no attention to the man behind the curtain

Since the floor is mine, I think I will mop it shiny with some Mr. Clean...
-------------------------------------------------------------------------------------------------------------------------

@ MH - I'm glad you learned how to use Google to help you learn things.
But you cannot take at face value the first equation you come across.
For the sake of humbling your argument that resistance does not matter,
We will suspend all forethought of Ohms Law.
And only consider the direct equations that apply specifically to an RLC circuit.

Your mistake here, is that you are considering the equation:
Wo = 1/ [(sqrt)LC] This is taken in Radians (not freq.)
What this represents, in terms of an RLC circuit, is the Natural Frequency.
This is the resonant frequency the circuit will assume without constantly driving the circuit.
When resistance is very low (not the case of the JT) it can be taken as an LC tank circuit.
If you have not noticed by now, a JT will NOT continue to resonate after the power is cut.


The resonant frequency of the RLC circuit when it is powered (driven) resistance, as a factor of Damping
as:  Damping Factor = Attenuation (in Nepers) / Wo (in radians).
This is most easily measured in the Joule Thief circuit as the Q factor.
the Q of the circuit = 1/R [(sqrt)L/C]

When Q is low, the circuit is "damped", and losses are heavy.
When Q is high, the circuit is "underdamped" and can oscillate,
 but there are inductive losses on the magnetic side.

When all components of the circuit are operating at a resonance
 that is also a resonant node of each components SRF
losses are minimized.



Using Kirchhoff's Voltage Law (Vr + Vl +Vc = V(t)): we can reduce the attenuation equation to a value ~ =
R/2L
(I know I said I would suspend Ohm's law, and Kirchhoff is basically the same idea, but this is necessary here)

Therefore, the 2 part equation, for the JT circuit is represented as
a=R/2L
and
Wo= 1/ [(sqrt)LC]

The proportionality between these two factors represents the Damping Factor.
And this can be taken as : 
Damping Factor = (R/2)[(sqrt)C/L]

Therfore, to determine Resonant Frequency, we are left with a Complex Frequency response (s),
part is the Natural Frequency, and the other part is the attenuation.
when s=jW ; where j is the imaginary part of the derivative -- the circuit assumes a sinusoidal steady state.

(peak) Voltage and current levels of the resonant waveform are defined by the relationship:
V(s)=I(s)(R+ L(s) + 1/C(s))

Admittance (Y) = 1/Impedance (Z) (inversely proportional)
Admittance Y(s) = I(s)/V(s) or s/L[s^2+(R/L)s +1/LC]

Now, looking ONLY at current, we find there is a Peak value of the function I(jW)
where (Wo) is also the natural resonant frequency.  Wo = 1/[(sqrt)LC]
It is important to note here, the peak value for Voltage; V(jW) derives a different frequency.

solving for Impedance with respect to frequency we find that:
Z = jWL + 1/jWC + R
By this analysis, we see that at the natural frequency; Wo=1/[(sqrt)LC]
Electrical Impedance peaks at a maximum.
However, Magnetic Reluctance (through the ferrite) at this frequency is NOT at a minimum.
Thus at Wo = 1/[(sqrt)LC], losses approach a peak. (not the maximum configuration, but quite high)


When the complex frequency is taken to be the resonant frequency of the circuit,
and this frequency is also a resonant node of the SRF of all components, such that s=jw
(making the assumption that the base voltage at this frequency is within the linear mode of the transistor)
we find peak (not max peak) amplitudes in both the current, and voltage within the frequency domain.
This represents a condition of maximum power transfer from the battery to the inductor, in a steady-state sinusoidal wave.

the resonant frequency of the feedback loop:
this is the current path through the resistor and coil presenting a reflection at the B-E junction of the transistor.
is defined as:

Wo = (sqrt)[1/LC - (R/L)^2] - note that the resistance value (R) is different from the resistance through the primary current path.

there is a 3rd current path in some configurations, that includes a factor of the batteries internal resistance,
I will not get into much more detail on that particular,
 as it can be represented as a loss constant pertaining to the battery.

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


**puts up the wet floor sign**













Pirate88179

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Re: Joule Thief 101
« Reply #209 on: February 14, 2016, 09:00:33 PM »
we can just "ignore" this 100k Ohm resistor


pay no attention to the man behind the curtain

Since the floor is mine, I think I will mop it shiny with some Mr. Clean...
-------------------------------------------------------------------------------------------------------------------------

@ MH - I'm glad you learned how to use Google to help you learn things.
But you cannot take at face value the first equation you come across.
For the sake of humbling your argument that resistance does not matter,
We will suspend all forethought of Ohms Law.
And only consider the direct equations that apply specifically to an RLC circuit.

Your mistake here, is that you are considering the equation:
Wo = 1/ [(sqrt)LC] This is taken in Radians (not freq.)
What this represents, in terms of an RLC circuit, is the Natural Frequency.
This is the resonant frequency the circuit will assume without constantly driving the circuit.
When resistance is very low (not the case of the JT) it can be taken as an LC tank circuit.
If you have not noticed by now, a JT will NOT continue to resonate after the power is cut.


The resonant frequency of the RLC circuit when it is powered (driven) resistance, as a factor of Damping
as:  Damping Factor = Attenuation (in Nepers) / Wo (in radians).
This is most easily measured in the Joule Thief circuit as the Q factor.
the Q of the circuit = 1/R [(sqrt)L/C]

When Q is low, the circuit is "damped", and losses are heavy.
When Q is high, the circuit is "underdamped" and can oscillate,
 but there are inductive losses on the magnetic side.

When all components of the circuit are operating at a resonance
 that is also a resonant node of each components SRF
losses are minimized.



Using Kirchhoff's Voltage Law (Vr + Vl +Vc = V(t)): we can reduce the attenuation equation to a value ~ =
R/2L
(I know I said I would suspend Ohm's law, and Kirchhoff is basically the same idea, but this is necessary here)

Therefore, the 2 part equation, for the JT circuit is represented as
a=R/2L
and
Wo= 1/ [(sqrt)LC]

The proportionality between these two factors represents the Damping Factor.
And this can be taken as : 
Damping Factor = (R/2)[(sqrt)C/L]

Therfore, to determine Resonant Frequency, we are left with a Complex Frequency response (s),
part is the Natural Frequency, and the other part is the attenuation.
when s=jW ; where j is the imaginary part of the derivative -- the circuit assumes a sinusoidal steady state.

(peak) Voltage and current levels of the resonant waveform are defined by the relationship:
V(s)=I(s)(R+ L(s) + 1/C(s))

Admittance (Y) = 1/Impedance (Z) (inversely proportional)
Admittance Y(s) = I(s)/V(s) or s/L[s^2+(R/L)s +1/LC]

Now, looking ONLY at current, we find there is a Peak value of the function I(jW)
where (Wo) is also the natural resonant frequency.  Wo = 1/[(sqrt)LC]
It is important to note here, the peak value for Voltage; V(jW) derives a different frequency.

solving for Impedance with respect to frequency we find that:
Z = jWL + 1/jWC + R
By this analysis, we see that at the natural frequency; Wo=1/[(sqrt)LC]
Electrical Impedance peaks at a maximum.
However, Magnetic Reluctance (through the ferrite) at this frequency is NOT at a minimum.
Thus at Wo = 1/[(sqrt)LC], losses approach a peak. (not the maximum configuration, but quite high)


When the complex frequency is taken to be the resonant frequency of the circuit,
and this frequency is also a resonant node of the SRF of all components, such that s=jw
(making the assumption that the base voltage at this frequency is within the linear mode of the transistor)
we find peak (not max peak) amplitudes in both the current, and voltage within the frequency domain.
This represents a condition of maximum power transfer from the battery to the inductor, in a steady-state sinusoidal wave.

the resonant frequency of the feedback loop:
this is the current path through the resistor and coil presenting a reflection at the B-E junction of the transistor.
is defined as:

Wo = (sqrt)[1/LC - (R/L)^2] - note that the resistance value (R) is different from the resistance through the primary current path.

there is a 3rd current path in some configurations, that includes a factor of the batteries internal resistance,
I will not get into much more detail on that particular,
 as it can be represented as a loss constant pertaining to the battery.

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**puts up the wet floor sign**

Wow, that is a lot more about this circuit than I even knew I did not know.  Thanks.

MH:

I always thought the JT was a tank circuit as I have always tuned mine to either the brightest light, or the lowest mA draw...these were never at the same resistance.  I thought, as Brad and others have said, that a coil has capacitance?  I have several JT's here that I can cut the input power to and the leds will continue to glow for more than a few seconds...not as bright as when the power was on but, certainly bright enough to see clearly so, that tells me the energy had to be "stored" somewhere right?  I had no other caps in the circuits which I am describing.  I always "assumed" that the stored energy was in the inductor and, if a device can store energy than it has capacitance right?

Those that know me know I am no electronics wiz by any means.  I have played and experimented with many variants of these circuits for about 7 years or so now, and I too am convinced that even the most basic JT has capacitance.

Am I wrong here?

Bill