Joule Thief 101

[tinman]

No back pedaling and thanks to me you now understand a Joule Thief better than you have ever understood one before in your life.

Your delusional MH.
If we all followed you,we'd still have wheels carved from rock.


Brad

[MileHigh]

No Brad, it's very clear now that a lot of your thoughts about how the Joule Thief operates were delusional.  Your "casual" remark about me needing to "understand" the "need for a variable resistor" in a Joule Thief has been blown out of the water and you were the person making a bunch of silly statements, not me.  You didn't understand the basics of how providing excess base current to an open-collector switching transistor configuration gains you nothing and you end up expending power needlessly with zero benefits.  You didn't realize that the voltage produced by the LED would be transformed back to the L2 feedback coil and give you a pretty decent EMF source for switching on the transistor and it would not be too sensitive to the decreasing battery voltage.  These are all insights into the operation of the Joule Thief that you didn't have the slightest clue about not to mention me correcting all of your mistakes and misconceptions and you have the gall to say that I am "delusional" and technologically regressive.

Instead of thanking me for all of this valuable information you stick to your little cardboard cutout character instead.

Before too long the issue of the resonance in the wine glass will be a done deal and then we can all see how the "resonant Joule Thief" project comes along.  Not too much information coming down the pipes on that one.  Then after that you can build yourself another pulse motor and demonstrate how you get "excess energy from magnets" and I won't be around to debate you, just believe whatever it is you want to believe and do your own thing.

[tinman]

So the vibe I am getting is that you have to learn how a Joule Thief operates from scratch.  No wonder you rejected those perfectly good YouTube clips that I linked to that explain how a Joule Thief operates.  You need to throw all of your preconceptions about the Joule Thief out the window and start with a blank slate and learn it all properly from the ground up.

Lol
Well one of us is going to have to start the learning process all over again,but i do not think it is going to be me

MH
I would like you to post again those claims i made that you deem to be incorrect.
When you have done this,i will post the video regarding those claim.
From there,we will then know who has to go back ,and start over.

I will be using your JT circuit for the test. We can then see on the scope the voltage across the LED,and the voltage at the base of the transistor.
We will also be measuring light output by way of a light meter as well.
We will use a battery with say around 900mV--so pretty dead.

So lets see who is right--lets see who has some learning to do.

Brad

[tinman]

Some quotes from MH--a recap of insults toward us that !dont! know what we are talking about.
A long read,but worthy of the time it takes to read.

When the transistor is acting like an ON-OFF switch, when it is ON and the battery voltage is constant, in the case of a 1K-ohm base resistor, or in the case of a 700-ohm base resistor, there will be no increase in current flow through the inductor, it will be the same. The factor that is limiting the current flow is the resistance of the inductor, it has nothing to do with the amount of base current flowing into the transistor.
In addition, if the battery voltage is 1.2 volts, then the maximum current flowing through the coil will be proportional to (1.2/coil_resistance).  If the battery voltage decreases to 1.0 volts, then the maximum current flowing through the coil will be proportional to (1.0/coil_resistance).  Therefore, there will be a decrease in the maximum current flow through the coil when the battery voltage is lower, resulting in a decrease in the initial current flow through the LED and therefore a dimmer LED for a lower battery voltage.

You can increase the current flowing into the base of the transistor, but it will just be "wasted current" that does nothing because the transistor is already fully ON.

The current flow though the inductor (a.k.a. the "magnetic field") will principally be controlled by (battery_voltage/inductor_resistance) because when the transistor is switched fully ON, there is a very low and constant voltage drop across the collector-emitter junction and that collector-emitter voltage drop will be the same if you switch the base resistance from 1K-ohm to 700 ohms.

Now, your words come back to haunt you.  You don't really know how a transistor works.

You have heard me complain about the "continuous affirmation" environment that you guys set up for yourselves, and the "Straitjacket of Agreement" where you are all paralyzed and can only agree with each other like a bunch of bobbing rubber ducks in a pond.

And look at the results.  Combine the "continuous affirmation" and the "Straitjacket of Agreement" and the bobbing rubber duckies and your "I am Brad and I am never wrong" and "I am Brad and I take the lazy route when I can" attitudes and here you are six years later and you can't properly analyze a basic switching function in a five-component circuit like a Joule Thief, nor do you truly understand how a Joule Thief works..

Instead, you play this ridiculous trash talk game and you are as fake-ass as a three-dollar bill

Some operational quotes from the expert.

As you increase the current flowing into the base input of the transistor because of a decreased value of base resistor, that represents expending more energy to switch on the transistor than you have to.  If you put more current than you need to though the L2 coil, than that means that the battery can supply less current to the L1 coil (when factoring in a higher battery output impedance for a nearly dead battery), and that translates into less energy available to light the LED.

I have already stated that when the battery voltage has dropped, you can't escape the simple V/R limiting factor for the amount of current that can be induced to flow through L1, and that means less current to light the LED.  Even if somehow the transistor stays on longer, the V/R current limiting factor is what really counts and the LED will be dimmer.

Saying "XX current is not enough current to fully switch on the transistor" is just you revealing that you don't understand the issues around how a transistor switching circuit works like I already stated.  Perhaps go to Amazon and do some online shopping.

Your comment above is wrong, and it shows that you don't truly understand how a Joule Thief works.  I hate to say it and it probably infuriates you but it is the truth.  What you need to do is take those lemons, educate yourself, and turn them into lemonaid.

The base current is added to the emitter current, not the collector current.  Assuming that the transistor is fully switched on then the resistance of the L1 coil is what determines the limiting factor for how much current passes through L1.

No, no, no, no, and no.  This is just you blindly believing that "more base current equals more inductor current."  You are completely ignoring the V/R current limiting factor assuming that the transistor is fully switched ON.  This is basic basic stuff and I have covered this point a few times in these postings.  You need to take a step back and really think about this stuff.

I think that enough has been said to make the point that your statement quoted above is wrong.  It's just a bunch of fake swagger and you not truly understanding all of the switching issues around a Joule Thief circuit.  A standard Joule Thief circuit is designed such that a conscious decision is made for the value of the base resistor.  There is no point in lowering the value of the base resistor beyond a certain point.  There is a relationship between the large-signal gain of the transistor, the resistance of the L1 coil, and the EMF that L2 presents to the base resistor that allows the Joule Thief designer to make a conscious decision for the value of the base resistor and clearly you are not aware of these issues.  Hence I strongly advise you to get a mastery of basic transistor switching circuits

Lowering the value of the base resistor will not fundamentally change the brightness of the LED because it's the battery voltage itself that is the primary factor in determining the brightness of the LED.

This is just you demonstrating your limitations again, the base current has no effect on the inductor current..

It's like you are learning how a Joule Thief operates from scratch here, because whatever you were thinking is clearly wrong.  Knowing your character, this is par for the course and you have been playing with Joule Thieves for years and not truly understanding how they operate.

So the vibe I am getting is that you have to learn how a Joule Thief operates from scratch.  No wonder you rejected those perfectly good YouTube clips that I linked to that explain how a Joule Thief operates.  You need to throw all of your preconceptions about the Joule Thief out the window and start with a blank slate and learn it all properly from the ground up.

See how you become mentally lazy and how that is part of your downfall when it comes to understanding the Joule Thief?  You are breaking the Kirchhoff Current Law for a bloody transistor and you don't give a damn.

Law you say

These are subtleties about the operation of the Joule Thief circuit that escape you.

So you are just stalling and faking because you don't want to be exposed for this gaffe. If not, then prove me wrong and I will be happy to listen to you make a solid argument discussing the electronics of the standard Joule Thief and how lowering the value of the base resistor for a constant battery voltage will supposedly make the LED brighter.

the transistor will not stay switched on longer, you are making a totally blind and completely wrong assumption based on your false belief that the transistor has been switched on "harder" and "'harder' equals 'stay on longer.'"
- since the transistor will not switch on longer, there will not be any "maintaining a magnetic field of the same value as the battery voltage drops."

So, you are showing the world that you don't understand how a Joule Thief works.  You are showing the world how you made a blind "Doh!" assumption that lowering the base resistance would increase the brightness of the LED.

So how lost are you Brad when it comes to the Joule Thief?

Well MH--not as lost as you.
It is time for you to retract all your !once again! incorrect comment's.
It is time you stopped posting until you go back to the start,and learn the difference between what you read in your book's,and what the reality actually is.
It is time for you to learn the truth--as i have-->on the bench.
It is time for you to eat some humble pie <H

https://www.youtube.com/watch?v=v9tsvbkOeW8


Brad

[MileHigh]

Some quotes from MH--a recap of insults toward us that !dont! know what we are talking about.
A long read,but worthy of the time it takes to read.

Some operational quotes from the expert.

Law you say

Well MH--not as lost as you.
It is time for you to retract all your !once again! incorrect comment's.
It is time you stopped posting until you go back to the start,and learn the difference between what you read in your book's,and what the reality actually is.
It is time for you to learn the truth--as i have-->on the bench.
It is time for you to eat some humble pie <H

https://www.youtube.com/watch?v=v9tsvbkOeW8


Brad

Yeah, after being on the bench for six years you are not only eating humble pie, you are manufacturing humble pie in mass quantities.  The clip is awful, an embarrassment.