Joule Thief 101

[MileHigh]

Okay, let me bounce this one back at you.

For starters, almost the entire world economy now depends on transistors, capacitors, and inductors.  Take those three things away, and we would have to deal with the fact that there is 3-5 days worth of food available before starvation sets in.  There is a huge magnetics industry.  You can say that every single computer motherboard built in the last 15 years relies on pulsing inductors to generate different voltages.  Design teams that design basic components like this do their best to approach what they know an ideal inductor can achieve.

I am no aeronautics guy, but let's say there is an ideal lift and drag for a wing design if you assume perfectly laminar air flow over the wing.  However, in the real world you don't have perfectly laminar air flow.  So the design team can compare the theoretical ideal numbers with the real-world numbers they are getting and then iterate on that and tweak their wing design and try to approach the ideal numbers.  So if they know the ideal numbers they will know how close their design is compared to the ideal.

Countless performance measurements are compared against theoretical ideal performance numbers so that designers know how well their designs are performing.

Beyond that, anybody that studies electronics learns about ideal capacitors and inductors.  It's the path towards understanding real-world capacitors and inductors.  I am truly fed up with this "what good is an ideal inductor" debate.  It's the way electronics works in the real world, and to truly understand real capacitors and real inductors you must understand ideal capacitors and ideal inductors, period.

When I read between the lines in some of the comments I am hearing, "That's hard, I don't want to deal with it, let me play with my coils and leave me alone."  It's a cop out and if you want to play with coils, being able to deal with very simple ideal coil scenarios and understanding them is extremely important.  You can apply that knowledge in the real world.

[tinman]

It's time to get real Brad.  The real coil and the ideal coil both produce equal CEMF to counter the EMF applied by the voltage source.

How does either type of coil respond to the EMF?  Continuously increasing current flows through the coil as long as the EMF is applied.  The CEMF is a direct result of increasing current flowing through the coil.  That's how a bloody inductor works!

Get yourself out of this quagmire and move forward and try to answer the question.

Yes,and normally the voltage across the coil would drop as current starts to flow--but you have an ideal voltage,and so it dose not drop.

You need to brush up on what an ideal coil is MH,and stop thinking in terms of real coils/inductors.


Brad

[Magneticitist]

To properly use an ideal inductor you would need to use constants in place of the rest of the parts,, you can turn those components of the normal real world item into ideals as well.

So with the inductor you would have an inductance value set, then you would have a resistance value set and then a capacitance value,, now you can change these values independent of the others to find the optimum values for what it is you are designing for.

The ideal model is a tool,, you can use the tool to get the best that you can,,

somewhere in MH' effort to help us understand his point, there is a real good lesson to be learned I just think it could be portrayed in a way where we could have the ability to see in real life how similar the math was to the real world outcome.. it's like the famous experiment where Lewin calculates where a swinging bowling ball looking weight is sure to stop at x time provided at random by his students (or something along those lines I don't quite remember)... how cool is it to see the real world result match the math? or when he showed conservation of energy, him place his face right in front of a swinging weight as you see the math work out in the real world?

[minnie]

  Let's call the current kinetic energy, imagine a rolling ball on a level surface,
  if there's no friction it'll go forever.( Inductor no resistance) once you add resistance
  it will slow down and stop,the higher the resistance the quicker it stops.
     Let's look at an ideal power supply, call it the Atlantic Ocean, call the level the
   voltage, take a cupful out and you're not going to notice much difference.
     An Ideal inductor WILL do what Henry says and react to a change in CURRENT.
    Each Henry will be what he says, a change of an Ampere in a second or however
   the definition goes.
      Take a schematic, how would you treat an inductor? At a basic level as ideal. After
    that you'd have to go to the specs and the calculations are going to be a lot harder!!
             John.

[tinman]

It's time to get real Brad.  The real coil and the ideal coil both produce equal CEMF to counter the EMF applied by the voltage source.

How does either type of coil respond to the EMF?  Continuously increasing current flows through the coil as long as the EMF is applied.

Get yourself out of this quagmire and move forward and try to answer the question.

As i said MH,you need to understand what ideal means.
In an ideal inductor,the CEMF would be equal and opposite to the EMF--ideal.

The CEMF is a direct result of increasing current flowing through the coil.  That's how a bloody inductor works!

And the CEMF apposes that which created it,and in an ideal situation,that CEMF is equal and opposite to the EMF.

Why is it so hard for you to understand what !ideal! means.

Maybe you should choose your words a little more carefully when asking a question.
Show me a circuit designers use with just an ideal coil. You will find they always add a series resistor in there design to mimic the resistance of a real world inductor.

If a simulator can simulate any real world circuit,why dose it crash when trying to simulate the operation of just an ideal inductor ?,why the need to add a series resistor to get the sim to run the simulation?
Why can you calculate the values and operation of your ideal inductor,and yet the sim crashes?.


Brad