Joule Thief 101

[tinman]

Brad:

We are back to where you agreed to do what I requested of you:  Describe how a standard Joule Thief circuit works.  Standard Joule Thief, standard circuit, standard running voltage, no bait and switch, no stream of consciousness.  Keep your mind focused on a single task.

Now are you capable of doing that or not?

MileHigh

What is a joule thief.

A joule thief is a minimalist Armstrong[1] self-oscillating voltage booster that is small, low-cost, and easy to build, typically used for driving light loads.

It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged (or "dead"); hence the name, which suggests the notion that the circuit is stealing energy or "joules" from the source. The term is a pun on the expression "jewel thief": one who steals jewelry or gemstones.

The circuit is a variant of the blocking oscillator that forms an unregulated voltage boost converter. The output voltage is increased at the expense of higher current draw on the input, but the integrated (average) current of the output is lowered and brightness of a luminescence decreased.

The name "Joule Thief" was coined by Clive Mitchell[3][4] and given to his variant of Kaparnik's circuit which consisted of a single cell, a single BC549 NPN transistor, a coil with two windings, a single resistor (typically 1000 ohms), and a single white LED. Clive originally named the circuit "Vampire Torch", because it sucked the last remnants of life from a battery.

At lower supply voltages a different mode of operation takes over: the gain of a transistor is not linear with VCE. At low supply voltages (typically 0.75 V and below) the transistor requires a larger base current to maintain saturation as the collector current increases. Hence, when it reaches a critical collector current, the base drive available becomes insufficient and the transistor starts to pinch off and the previously described positive feedback action occurs turning it hard off.

I dont know what planet your on MH,but a JT circuit is designed to drain the remaining energy from batteries that would otherwise be considered dead. So,i will only be describing how the (your) JT circuit works during the operation at voltages we would see when draining the last remaining energy from a dead battery--not MH's new battery blocking oscillator.

But we can take a poll if you like MH,and if more people here agree that they want to use a JT just to light an LED on a  healthy/charged battery,rather than be able to drain the life out of all there dead batteries,then we will go your way MH,and you lead the way in making the new single 1.5 volt battery cell torch.


Brad

[MileHigh]

Magluvin:

"What I have a hard time understanding, MH:
is why you are so adamantly against such attempts to improve efficiency in this manner."

I have been trying to be social with mh lately. I used to feel the need to hammer the same thoughts that you have written above to him many times before. Im afraid we cant fix that. So I just stay off that battlefield because it takes toooo much time and thread space to just end up with what we see today. Its not only the constant insistence that an 'idea'(s) will not work, but topping it all off with degrading insults doesnt fare well with me either. I have written a few reply posts in the last couple weeks that once I reread and thought about it, I just deleted them instead of falling in a never ending dual that doesnt account for much but a couple of hot heads..

We will take a reality check on this one.  You will not find a single statement by me saying that I am against improving the efficiency of a Joule Thief.  So why are you agreeing with him?  Of course between the lines in Smoky1's statement is that "Smoky1 is attempting to bring increased efficiency to the Joule Thief by preaching that "resonance" will make a Joule Thief more efficient so if you challenge Smoky1 then you are 'against such attempts to improve efficiency.'"  But Smoky1 has only talk to offer that you have seen many times before so why would you agree with him before he has shown any evidence that his pitch is real?

Don't do the "degrading insults" play.  If you read me carefully I never take a first step in that direction, never.  Tinman and I are "fighting" over how a Joule Thief works.  If he says something nasty I might respond, but I am never the initial aggressor.  If his behaviour shows some attributes that are not conducive to an orderly understanding of how a circuit works and he is all over the map and it gets frustrating, I will call him out.  Your own record on "degrading insults" is one of the worst on this forum and I assume that you have thought long and hard about that as well as thinking about the whole raison d'être for this forum which had you doing some soul searching about how much time to invest in "the search."  I commend you for that.  Your one-time tag-team "partner in crime" is getting serious push-back on EF for his horrible behaviour and people are openly expressing how unacceptable it is.  I only wish other people on this forum challenged you and your tag-team partner when it was absolutely horrible around here.  It's the one time that the people on EF have outshone the people on OU and demonstrated some backbone and character.  Again, don't put the "degrading insults" label on me because it is not true.  It's just another cynical card to play.

The gist of it is this:  People have to get past the back-slapping and mutual stroking when discussing simple circuits in fake imaginary terms that actually don't make sense in real life.  That's is what was happening about the Joule Thief.  I made my case and got push-back, and then I pushed-back.  There is nothing wrong with that.

So you got a nearly 1 MHz sine wave on your scope display.  What next?  That's the hard part and I wish you luck.  What you want and need to do is figure it out just like I annotated your scope shot for the regular Joule Thief.  You have to do that to see where it is going to lead you.  Will it be a dead end or "improved efficiency through resonance?"

MileHigh

[tinman]

 author=MileHigh link=topic=8341.msg474813#msg474813 date=1455896984]

Brad:
The reason I am emphasizing the "WORK" angle is because this was your "explanation" for how your "Cool Joule" feedback oscillator circuit worked:  "Miller effect."

Your explanation for your "Cool Joule" circuit's operation is a joke.

A Joke--really
I just explained as to how it was able to still oscillate with no inductive coupling between L1 and L2--not the whole operation process.
Let me guess--you are full bottles on it,even though you probably have never looked into it's operation?-->do tell.


Brad

[MileHigh]

Brad:

I dont know what planet your on MH,but a JT circuit is designed to drain the remaining energy from batteries that would otherwise be considered dead. So,i will only be describing how the (your) JT circuit works during the operation at voltages we would see when draining the last remaining energy from a dead battery--not MH's new battery blocking oscillator.

It's just a question of not being all over the map.  The Joule Thief has two operating modes.  The first one is defined and it's operation is understood.  It is not in any way, shape or form an "RLC oscillator" like you stated, you were dead wrong.

Do you agree with my description of how a standard Joule Thief operates or not?  If you disagree then please do your explanation for how it operates like you said it would.

The Joule Thief obviously changes the way it works at low voltages and it has not been properly explained by anybody at all.  Don't you dare try to pull off another bait and switch and say, "When I sad RLC oscillator I meant at low voltages" or "I have been talking about this mode of operation the whole time."  I am truly sick and tired of your bait and switch bullshit.

You want to tackle the low-voltage operation where the standard digital switching mode with nice clean energizing and discharge cycles breaks down and the way the transistor works and presumably the way the feedback system works completely changes into some new mode of operation?  If yes then go for it.

MileHigh

[tinman]

Magluvin:

We will take a reality check on this one.  You will not find a single statement by me saying that I am against improving the efficiency of a Joule Thief.  So why are you agreeing with him?  Of course between the lines in Smoky1's statement is that "Smoky1 is attempting to bring increased efficiency to the Joule Thief by preaching that "resonance" will make a Joule Thief more efficient so if you challenge Smoky1 then you are 'against such attempts to improve efficiency.'"  But Smoky1 has only talk to offer that you have seen many times before so why would you agree with him before he has shown any evidence that his pitch is real?

Don't do the "degrading insults" play.  If you read me carefully I never take a first step in that direction, never.   If he says something nasty I might respond, but I am never the initial aggressor.  If his behaviour shows some attributes that are not conducive to an orderly understanding of how a circuit works and he is all over the map and it gets frustrating, I will call him out.  Your own record on "degrading insults" is one of the worst on this forum and I assume that you have thought long and hard about that as well as thinking about the whole raison d'être for this forum which had you doing some soul searching about how much time to invest in "the search."  I commend you for that.  Your one-time tag-team "partner in crime" is getting serious push-back on EF for his horrible behaviour and people are openly expressing how unacceptable it is.  I only wish other people on this forum challenged you and your tag-team partner when it was absolutely horrible around here.  It's the one time that the people on EF have outshone the people on OU and demonstrated some backbone and character.  Again, don't put the "degrading insults" label on me because it is not true.  It's just another cynical card to play.

The gist of it is this:  People have to get past the back-slapping and mutual stroking when discussing simple circuits in fake imaginary terms that actually don't make sense in real life.  That's is what was happening about the Joule Thief.  I made my case and got push-back, and then I pushed-back.  There is nothing wrong with that.

So you got a nearly 1 MHz sine wave on your scope display.  What next?  That's the hard part and I wish you luck.  What you want and need to do is figure it out just like I annotated your scope shot for the regular Joule Thief.  You have to do that to see where it is going to lead you.  Will it be a dead end or "improved efficiency through resonance?"

MileHigh

Tinman and I are "fighting" over how a Joule Thief works.

It would seem to me,it's more of an argument as to the JT is suppose to do,and what we want it to do. You want it to be used at voltages where you have a standard blocking oscillator operation,were as!i believe! the rest of us wish to use it to drain nearly dead batteries all the way down.  This is what the JT is used for mostly MH,so why should we be looking at how it operates at higher voltage supplies?.


Brad