Joule Thief 101

[Magluvin]

Do you need an answer to understand the need for a variable base resistor MH?-or will your batteries simply remain at the rated voltage of 1.5 volt's?.
That was a bit of a silly statement by your self MH.

Asking why the need for resonance is also a silly question.
Try pushing a child on a swing both in and out of resonance,and see which uses more energy for less motion. Why can you jump higher on a trampoline with less effort,than you can on the ground with more effort?.

MH-are you board again?.


Brad

For example.  If a person of say 100lb is on a particular playground swing, and say it takes 2 seconds to swing a full 'resonant' cycle, then measure how much energy it takes to keep that cycle going.  Now try to apply input energy to make that same person on the same swing complete that same cycle in .5 seconds. It will definitely take more energy in to run that swing at .5 second cycles because there would need to be a constant control from the input, of which in my mind would be a tremendous amount of energy to accomplish compared to the input of the 'resonant' 2 second cycle.  Or even a 5 second cycle. The input would have to apply some kind of 'constant control over the course of the cycle, including 2 places in the cycle of  braking and 2 places in the cycle of pushing up from the low position, once for each direction.

It is very clear that the input energy at 2 seconds per cycle would be minimal compared to forcing a .5 second or a 5 second cycle

To repeatedly hear that operating anything at resonance has no advantages over operating everything out of resonance, sounds a bit out of fiction instead of reality.

Like how many ways can it be described.  Can an am radio pull in music from 910khz while tuned to 1200khz? How about when the radio is right next to the transmitter of the 910khz station? It takes a lot more input to do such a thing. When I was a kid with my radioshack electronics kits, if I had made an am radio with an audio amp circuit to hear it better, and tuned into a very local station, the audio was loud and clear. But even if I just put an ant on the input of the amp alone, I could hear the same radio station, but it wasnt nearly as loud as with the am tuner connected.

Mags

[MileHigh]

Do you need an answer to understand the need for a variable base resistor MH?-or will your batteries simply remain at the rated voltage of 1.5 volt's?.
That was a bit of a silly statement by your self MH.

Asking why the need for resonance is also a silly question.
Try pushing a child on a swing both in and out of resonance,and see which uses more energy for less motion. Why can you jump higher on a trampoline with less effort,than you can on the ground with more effort?.

Brad

No, that won't cut it Brad.  Don't try to play the "It's so obvious that I don't have to explain it" game.  Right now you are the one making the silly statements.  The Joule Thief is an electronic circuit and if you are stating that you need a variable base resistor for it then you must have an explanation and one or more reasons for saying that.  I would like to hear why you need a variable base resistor.

Requesting the requirement for resonance is a perfectly sensible question.  I will remind you that nobody here can even explain how a Joule Thief operates "in resonance."  That is a fact.  At this point nobody even knows what they are talking about or can explain what it even means.  The best we have so far is that Smoky2 said "tweak the base resistor and look for a sine wave."  Seeing a sine wave doesn't necessarily mean you are in resonance.  Plus like I already said, if you are looking at high frequency signals in a circuit, they all eventually become sine waves.

The child on a swing is a failed analogy and I will cover that in my next posting.

The whole point of this is to deal with real electronics and to stop repeating cliches that don't mean anything and to stop going down garden paths and blind alleys.

I would like to hear your explanation for the Joule Thief.

MileHigh

[MileHigh]

For example.  If a person of say 100lb is on a particular playground swing, and say it takes 2 seconds to swing a full 'resonant' cycle, then measure how much energy it takes to keep that cycle going.  Now try to apply input energy to make that same person on the same swing complete that same cycle in .5 seconds. It will definitely take more energy in to run that swing at .5 second cycles because there would need to be a constant control from the input, of which in my mind would be a tremendous amount of energy to accomplish compared to the input of the 'resonant' 2 second cycle.  Or even a 5 second cycle. The input would have to apply some kind of 'constant control over the course of the cycle, including 2 places in the cycle of  braking and 2 places in the cycle of pushing up from the low position, once for each direction.

It is very clear that the input energy at 2 seconds per cycle would be minimal compared to forcing a .5 second or a 5 second cycle

To repeatedly hear that operating anything at resonance has no advantages over operating everything out of resonance, sounds a bit out of fiction instead of reality.

Sure, let's take the swing as an example but let's get real about it and also talk about a real output.  Without having a real output you are just spinning your wheels and going nowhere.

For starters, resonance is simply a method for storing energy.  So you have to put energy into the resonant system, and by definition take energy out of the resonant system if you are going to accomplish something.

What you can't do is not keep your eye on the energy ball, and I don't think either of you are doing that properly.

The child is at rest on the swing.  You give him regular pushes of 20 joules.  The swinging gets higher.  The child's swing energy goes something like 20 joules, 40 joules, 60, 80... 180, and then finally there is 200 joules of energy stored in the swinging.  Energy that you put there by pushing on the child.  So far the output is zero.

Now that the child is swinging high, let's factor in the air resistance.  Let's say the child loses 5 joules per swing.  So that means you only have to push with 5 joules of energy per swing to maintain the high swinging, and the output is still zero.

So, now let's talk about an output - you have to have an output.  So let's say that next to the swing there is a hanging rope that loops down and the child is wearing a leather work glove in one hand and he grabs the rope during each down swing to slow himself down and burn off some energy.  Let's say he burns off 30 joules every time he grabs the rope.

So, you push on the child with 5 joules, and he is one the way down with 200 joules of energy in the swing.  But this time he grabs the rope and when he comes back to you on the reverse swing there is only 165 joules in the swing.  So that means that this time you can't get away with pushing with 5 joules because of "swing resonance magic," you will have to push back with 35 joules of energy to maintain the swinging.

Where is the "resonance magic" there?

When the child is swinging to output 30 joules you have to input 35 joules.

If there is no swinging and you just grab the rope and pull on it, to output 30 joules you have to input 30 joules.

Exactly the same thing will happen in an LC resonant circuit.  The friction looses when swinging will be substituted for the i-squared-R losses in the wires.

So forget about your trampolines and your resonant frequency stuff, it means nothing.  Look at the energy and you will find nothing special.  It's just another wild goose chase down a garden path.

MileHigh

[Magluvin]

I will remind you that nobody here can even explain how a Joule Thief operates "in resonance."  That is a fact.  At this point nobody even knows what they are talking about or can explain what it even means.

Well I wouldnt say that. So far I just have not gotten up to the resonant freq of the transformers Ive tried.   That is so far.  So that deafening silence you are speaking of is not me backing off because of your statements. As I did post that I will be back on it after the weekend when I finish this car audio system.

This week Im winding several different winding configs and doing some 1 shot power disconnects of the windings, where the scope will catch and display as a single shot, then spread the ring wave across the screen so the scope will show the freq. Did this with a pulse motor coil, and it will work here. This will give me the target freq I need to get the circuit to operate.

Now that I have the scope I want to revisit multi core transformers. If we wind a primary on a core, then wind a secondary through the primary core and a secondary core, if the primary is in resonance, loading the secondary wont disturb the primary resonance. I still have a few of those projects in a box.



Mags

[sm0ky2]

  Is it possible that your supercapacitor is self-charging?

this is always a possibility, with certain types of capacitors in certain situations.
Tantalum capacitors can be exploited in this manner.
I have not had a chance to play with these new "supercaps"
but it is indeed possible that they may under the right circumstances, display this phenomenon.
Some electrolytic capacitors are designed NOT to do this, for stability purposes.