Joule Thief 101

[tinman]

Tinman,

Have you used or are you familiar with LtSpice? Are you aware there are many various parameters that can be set prior to running a simulation not including the circuit parameters? I can simulate the 5h inductor with a dcr of 1 fohm (1e-15) without crashing so obviously Poynt and I are using different operating parameters. For example, in this particular simulation I am using modified trap for the integration method with the other options being trapezoidal or gear.

Does this possibly change your opinion about simulating this ideal inductor?

Poynt,

I would like to know what parameters you are using to replicate your crash condition.

partzman

No,i am not interested in simulators,i am a hands on man that works with real devices.
Yes,you need to add a resistance to get your sim to work,and as soon as you add that resistance,you no longer have an ideal inductor. You may think it is close,but even that small amount of resistance makes an infinite difference--in other word's,your resistor value looks extremely large as far a a zero resistance value is concerned. You might as well have taken a cup of water from the ocean. To see the difference,take a look below at the screen shots at what ohms law has to say about a very small resistance value ,against no resistance.

Try and get your sim to simulate an ideal inductor(no resistance)--it never will,because like the real world,there needs to be an imperfection added.

Run your sim for 100 seconds like poynt did,and see if the voltage drop's as the current rises--just as a test


Brad

[partzman]

Try and get your sim to simulate an ideal inductor(no resistance)--it never will,because like the real world,there needs to be an imperfection added.

Run your sim for 100 seconds like poynt did,and see if the voltage drop's as the current rises--just as a test


Brad

Brad,

I ran the sim for 100s and attached the results below which came out as expected. Using delta I = E*t/L = 4*100/5 = 80 amps. The voltage drop due to this peak current is E = I*R = 80 * 1e-15 = 8e-14 volts which is so small that it doesn't show up on the V(Vin) cursor which indicates 4 volts at the end of the simulation.  The netlist is shown to prove the sim was run with a dcr = 1e-15.  The timestep used is 10us instead of the previous 1us so the sim completed in a reasonable time.

Now let's reason together on this basic issue. If I understand your position correctly, one could logically assume that the initial current in this example at T=0 when the 4 volts is applied would be I = E/R =4/1e-15 = 4e15 amps. This follows your logic that with a dcr = 0 ohms, the current at T=0 would be infinite.  So, as we back off 0 ohms or IOW add an infinitesimally small amount of resistance, the current would no longer be infinite but some finite value following I = E/R.

But this is not what the sim shows which agrees with the real world.  Why is this? Because of the self inductance of the coil. IMO, with a dcr = 0, a coil is a pure inductor and still operates as such.

partzman

[MileHigh]

<<< In short MH,, your inclusion of a zero resistance and a zero capacitance was incorrect, you should of asked what they would need to be to match the rating you provided and from there what the rise time or whatever would look like. >>>

No, this is nonsense and foolishness that both you and Brad seem to be subscribing to without any rhyme or reason.  Just like Brad claims that "the inductor is producing current equal and opposite to the ideal voltage source so the current is zero and infinity at the same time" or whatever.  The inductor is producing squat, it's a passive standard circuit element.

This is nothing more than a refusal to learn and willful ignorance and some kind of hokey superstitious belief system plucked from who knows where or what or when.  Just believing that you are right for whatever strange reason does not make it right.

This is just another senseless and ridiculous argument that is hindering progress with respect to the question and actively destroying the learning process for the participants and for those that are reading and want to learn.

[Magneticitist]

<<< In short MH,, your inclusion of a zero resistance and a zero capacitance was incorrect, you should of asked what they would need to be to match the rating you provided and from there what the rise time or whatever would look like. >>>

No, this is nonsense and foolishness that both you and Brad seem to be subscribing to without any rhyme or reason.  Just like Brad claims that "the inductor is producing current equal and opposite to the ideal voltage source so the current is zero and infinity at the same time" or whatever.  The inductor is producing squat, it's a passive standard circuit element.

This is nothing more than a refusal to learn and willful ignorance and some kind of hokey superstitious belief system plucked from who knows where or what or when.  Just believing that you are right for whatever strange reason does not make it right.

This is just another senseless and ridiculous argument that is hindering progress with respect to the question and actively destroying the learning process for the participants and for those that are reading and want to learn.

I have never personally believed you to be absolutely wrong, I just personally disagree with the logic behind 0 resistance in the real world so far. And so far, I don't see how any math or sims can provide us the absolute answer. That has absolutely nothing to do with the potential faith I can put into you knowing what you're talking about regarding any other scenario regarding an R value that is not absolute 0. If we were all discussing an R value that is ANYTHING other than 0, this would not be so frustrating.

So I don't see why you feel the need to get offended or lose patience.  It's not like anyone is saying, "Oh wow, you ACTUALLY think that? you must have no idea what you're doing in any other equations then"..

It's more like, "wait.. are you ACTUALLY saying you know for sure what would happen in the real world with your 5h R=0 inductor?"  this is because, I can't really tell to be honest, but it seems like you are saying that with the confidence that it is more than hypothesis..

you said " Just believing that you are right for whatever strange reason does not make it right."

Isn't this what the argument is really about?

[MileHigh]

No MH,, it is not a refusal from me to learn.

Because at resistance =0 the amps are infinite and you do not have a change of any sort when you are using a percentage of infinite, or any partial value of infinite because they are all infinite.

The reasons the sim needs a small resistance was explained by Poynt, myself, and perhaps Partzman.  So that amounts to a refusal on your part to learn.

Believing that stating that the amps will go to infinity when the resistance is zero is nothing more than you cloning Brad.  And what does that mean?  It means that right now both of you don't have the slightest clue what inductance means, or how an inductor, real or ideal, behaves.

So you have a choice, keep parroting or try to learn what this subject matter is all about.