Joule Thief 101

[tinman]

The problem with your explanation for the specific alternative circuit shown by Tinman, is that , at turn on, no current can flow through the collector junction until the base has been turned on, and by your explanation the base cannot turn on, because no current is induced into the coil that feeds, because no current can flow through the collector coil while the collector junction is open, until the base turns on.

There is no direct source voltage coupling to trigger the base because there is no direct DC connection to the base, only an inductive connection which requires current through the collector coil. A severe case of chicken and egg, unless their is something else in the circuit momentarily allowing the base to initially trigger. That initial trigger mechanism lies in the tiny capacitance in the transistor junction.


Cheers

Thank you Hoptoad.
It is good to see some one is on the ball here.
The 2n3055 BC capacitance can get as high as 700pF. This is more than enough to start the transistor conducting.

Internal capacitances are due to the storage of charge at the PN junction's. These PN junctions act just like the plates of a capacitor,where in they can store charge. This stored charge is enough to trigger the transistor when in circuits like my cool joule circuit. This is where the miller effect kicks in,and this stored charge is what switches the transistor on. This charge exist weather or not the transistor is being pulled on harder by a second current input source--such as MH JT circuit. This is the C in the LRC circuit--it exists,and is there.
There is junction capacitance,and diffusion capacitance.
Junction capacitance-where the charge is stored in the depletion region of the PN junction.
Diffusion capacitance--quote wiki: Diffusion Capacitance is the capacitance due to transport of charge carriers between two terminals of a device, for example, the diffusion of carriers from anode to cathode in forward bias mode of a diode or from emitter to baseforward-biased junction for a transistor.
We do not have to worry to much about diffusion capacitance with everyday JT circuit's.


Brad

[MileHigh]

That's a complete and total fail Brad.  No bait and switch.  Why would a few hundred picofarads of capacitance affect anything?  It's just a rhetorical question.

Just explain to the readers how an ordinary Joule Thief actually works.  How does the timing work and how does the switching work?

The floor is yours.

[MileHigh]

Post #288 was edited and text was added in bold to address some of Brad's "objections."

Brad, in the last four or five postings you have dropped the line that you have "corrected my mistakes."

I already addressed this issue in an earlier posting when I said this, "So you are taking a counter-measure strategy where you are doing a "play."  The "play" is to try to feign that I am the one that doesn't understand what is going on, so you are asking me questions.  The backdrop to all of this is that I have been around long enough so that you, and nearly everybody else watching, already has a very decent idea what my knowledge level is."

So don't try to "play" me.  Just get on with it and explain to the readers exactly how a regular Joule Thief works with no muss, no fuss, no misdirection, no bait and switch, no "plays," and no shenanigans.

The floor is yours.

[tinman]

The floor is yours.

That junction capacitance is enough to make the transistor switch on,and a circuit to oscillate,where there is no inductive coupling between L1 and L2. Myself and many others have proven this,and was also confirmed by MarkE,and worked out by Vortex1. Are you going to argue with all them MH ?--i didnt think so.

Just explain to the readers how an ordinary Joule Thief actually works.  How does the timing work and how does the switching work?

I have given you two examples of ordinary JT circuit's,that have different operating parameters.
But before you burst a bubble,i will give a quick and simple rundown on the one below--seen as you like it so much. Why im doing this again,i do not know,because we have just spent the best part of 3 days trying to get you to describe the correct switching and operation of the JT circuit you provided.
What do you mean by timing MH ?. If you are referring to frequency,on times,off time's ETC,how can i possibly do that from a picture?. Where is all the information needed to calculate this?--battery voltage,torroid size and grade.wire size and type-ETC ?.
Or,if by timing,you mean how each event takes place for one complete cycle,then that is much the same as how it work's-is it not?.

Before i can give an accurate description of the operation MH,i will need you to provide some information on your transistor. I need to know the required base current and voltage for the transistor to start conducting. Without that,there is no way of giving an accurate operation description,as it can go two way's,and this depends the required current and voltage needed at the base to switch the transistor on. Even if we have the full 1.5 volt's on the battery,the base of the transistor will only receive a maximum current from the battery of 1.5 mA. So for example,if the 2n2222 needs 2mA of current at the base to switch on,then we need a 2v battery-which we do not have. So this would in turn drop the available base voltage down--see what i mean. So i need the required base voltage and current to switch on the 2n2222 transistor. Once you give me that,then i will provide the operation description you so much require.

Brad

[MileHigh]

Brad:

If you really believe that the transistor junction capacitance is relevant, then put it into your description.  The schematic shows a 1K base resistor and a 2N2222 transistor but that is not even relevant to the discussion.  Nor are the specifics of the toroid and the windings truly relevant to the discussion.

So don't get hung up on the details and use that as an excuse.  Or if you insist that you need these kinds of details (which you don't) then put in some reasonable values by yourself.

Descriptions of how circuits operate are done without needing to have component specifics all the time.  You saw how I posted three descriptions of how a Joule Thief operates and there were no component specifics.

I am looking forward to reading your complete description of how a standard Joule Thief works.

MileHigh