Joule Thief 101

[hoptoad]

A quick video on the circuit above.
The 10k VR has been omitted.
https://www.youtube.com/watch?v=eCnT6C7T81o
Brad

Perfect demonstration. Though, to really top it off you could have shown the 2n3055 in standard current control mode with a led connected to its collector back to a separate continual voltage source with a high enough voltage (3.6V?) to drive the led if the transistor turns on, and then connect your 236mV directly to the base. Connect with the emitter sharing the negative rail of each separate voltage source.

Obviously nothing will happen until you wind the 236mv up to 720mV. Comparative circuits really hit the message home. It would show clearly that without the L(& C) components of the circuit, nothing will happen until the base threshold voltage is attained. The ball's in MH court, but I think he'll just dribble with it rather than score any goals.

Cheers Tinman, keep up your enthusiastic exploration.

[MileHigh]

Okay Brad so you say I have gotten it all wrong and you say you are the one that is right.   You asked me how a Joule Thief works.  I have linked to videos and references from the web, and I have discussed various aspects of how a Joule Thief works throughout the thread.

Here is the main YouTube clip:  https://www.youtube.com/watch?v=0GVLnyTdqkg

Then look at the following postings:

230
255
257
258
267

Also post #197 and there is a small error in that post.

I state "Time constant #2 = Inductance/(Coil resistance + LED "resistance")"
It should read, "Time constant #2 = Inductance/(Battery resistance + Coil resistance + LED "resistance")"

Anybody that has a basic understanding of electronics will be able to understand how a Joule Thief works by reading the provided information and watching the main clip.  So there is your explanation.

So, since I supposedly have goten it all wrong, the YouTube clip must be wrong, and the web sources that I linked to must be wrong, and the information that I added above must be wrong.

Okay, here is your opportunity to get it right.  Please explain to the readers exactly  how a Joule Thief works using any sources of information you want.   That is the big issue.  I will be happy to respond to all outstanding questions that you have posed to me, but let's get the big stuff done first.

The floor is yours:  Please explain to the readers exactly how a Joule Thief works.

MileHigh

[sm0ky2]

Also post #197 and there is a small error in that post.

I state "Time constant #2 = Inductance/(Coil resistance + LED "resistance")"

It should read, "Time constant #2 = Inductance/(Battery resistance + Coil resistance + LED "resistance")"

MileHigh

your awareness of the battery resistance and how it affects the circuit is an important step in understanding all of the processes that are involved.
However one should not lose sight of the effects of the magnetic ferrite in this situation. It acts as a resistance in one instance, and a capacitance in the other.

[tinman]

Here is the main YouTube clip:  https://www.youtube.com/watch?v=0GVLnyTdqkg

Then look at the following postings:

230
255
257
258
267

Also post #197 and there is a small error in that post.

I state "Time constant #2 = Inductance/(Coil resistance + LED "resistance")"
It should read, "Time constant #2 = Inductance/(Battery resistance + Coil resistance + LED "resistance")"

Anybody that has a basic understanding of electronics will be able to understand how a Joule Thief works by reading the provided information and watching the main clip.  So there is your explanation.

and the web sources that I linked to must be wrong, and the information that I added above must be wrong.

Okay, here is your opportunity to get it right.  Please explain to the readers exactly  how a Joule Thief works using any sources of information you want.   That is the big issue.  I will be happy to respond to all outstanding questions that you have posed to me, but let's get the big stuff done first.

The floor is yours:  Please explain to the readers exactly how a Joule Thief works.

MileHigh

Okay Brad so you say I have gotten it all wrong and you say you are the one that is right.   You asked me how a Joule Thief works.  I have linked to videos and references from the web, and I have discussed various aspects of how a Joule Thief works throughout the thread.

And i have shown time and time again,that the cycle is not restarted by the battery--it just cannot once the battery voltage falls below the voltage required to switch on the transistor. Surely you understand this MH,or are you going to continually just copy and past incorrect information found on the internet ?.

It's a simple question MH--how is it that i have 720mV being delivered to the base of my transistor,and yet only have a supply voltage of around 250mV?. How can it be the battery(supply voltage) that is switching on the transistor ?.

So, since I supposedly have goten it all wrong, the YouTube clip must be wrong,

Yes,the youtube clip is wrong,and because you just believe in what some one else is telling you,then you to are wrong. Go and listen to your video again MH,right at the end of the first cycle-->5 minute mark,where he state's--Quote: Once the magnetic field is all gone,there is no more current for the LED,and it turn's off.And we wait for the battery voltage to start opening the base to emitter gate again,to start the whole cycle over again.

Now,with that information MH, please explain as to how the battery can open the base/emitter gate,when that battery voltage falls below the required base voltage of the transistor for it to switch on?.

Like i said,you,your video,and provided operation information are wrong,and i have show this a number of times now with actual working devices. It simply dose not work that way,and cannot work that way once the battery voltage falls below the required switch on voltage of the transistor.

Please go and do a little more research before providing more incorrect information.


Brad

[tinman]

your awareness of the battery resistance and how it affects the circuit is an important step in understanding all of the processes that are involved.
However one should not lose sight of the effects of the magnetic ferrite in this situation. It acts as a resistance in one instance, and a capacitance in the other.

I would also add smOky2,that the transistors junction capacitance also plays a vital role in the operation of most of the JT circuit's.


Brad