Joule Thief 101

[sm0ky2]

Do you see why?

[Johan_1955]

Do you see why?

Yes, and even better with the NPN Collector to the +, and Emitter to the coil, so the NPN above the Flipped Coil, and a small C over CE junctions.

[MileHigh]

Brad:

Credit where credit is due,you hit the nail on the head with that one.

And look at what you first said:

There is no death spike-you need to understand the circuit, and why there is a spike across L2 when the transistor becomes open. It all has to do with the number of turns on each coil-the more turns, the higher that L2 spike will be-there is nothing out of the ordinary with that spike.

Then you said:

It is not a massive anomaly,and is present in every JT--as seen in Mag's scope shot's.
You simply cannot work out why it is of a higher value in my setup.

It's all coming back now to bite you on the ass--and you are the one showing your own errors lol.

It's a never-ending slog with you.  It's like driving down a road with a continuous series of speed bumps, and even worse, "don't back up" road spikes pointed in your direction.  I am not going to be a bobbing duckie for you in a straitjacket, but I am also not going to do this kind of debate forever.  Once this is done I am jumping off the train and you can go back to doing your experiments and leading yourself down a garden path with your bobbing duckies all nodding in agreement.  Or I can hope that you become more open minded and get over this obsession with always being right no matter what.  That's for you to decide because I won't be around.

MileHigh

[MileHigh]

Getting back to the matter at hand...

Your "red dot" current flow speculation is incomplete for starters, and wrong.  If you are going to show current flow you have to show a complete loop of current.  The blue dots are correct like you speculated, with the exception of the blue dots that lead to the LED and then stop and go nowhere.  Like I said before the Joule Thief transformer is temporarily shorting itself out and burning off energy and stealing that energy away from the LED.  This whole time your Joule Thief has been crippled.

But what about during the off period,where now the current flow in L1 remains in the same direction,but the current flow through L2 is now in the opposite direction. Would not the magnetic field being built by the current flow in L2 now be additive to the magnetic field that is now collapsing in L1. Could this be the reason for the brighter LED when the base resistance is lowered,in effect raising the current flowing through L2.

When you get the reverse current flow that is an energy burn where energy is burnt off in the N-P collector-base junction and also in the base resistor.  So no go for a mechanism for making the LED brighter.

As I previously stated when you lower the base resistance, it's really a secondary effect that makes the LED brighter.  If we assume that for both a 1k base resistance and a 500-ohm base resistance that the transistor is "fully ON" (a.k.a. "hard ON") then the rise in current through L1 when the transistor switches on is identical in both cases.  However there is a secondary effect that makes the time period when the transistor remains on slightly longer, and that allows for a smidgen of increased current to flow through the L1 which results in an LED which is a smidgen brighter.

Now, we can't forget that your Joule Thief is not functioning properly.  So it would be worthwhile to repeat the variable base resistor tests after the problem has been fixed and see what the results are.  I am going to suspect we will see something similar with the LED slightly increasing in brightness for the same reasons.  And of course when the problem is fixed presumably the LED will be brighter overall.

MileHigh

[tinman]

quote]And look at what you first said:

MH
It is not a death spike at all.
It is in fact present in all JT circuit's--it's just that no one has taken any notice of it as of yet.
I have now tested 3 different JT circuit's,and it is present in all of them.
This !so called! death spike actually helps in raise the brightness of the LED.

It's a never-ending slog with you.  It's like driving down a road with a continuous speed bumps, and even worse, "don't back up" road spikes pointed in your direction.  I am not going to be a bobbing duckie for you in a straitjacket, but I am also not going to do this kind of debate forever.  Once this is done I am jumping off the train and you can go back to doing your experiments and leading yourself down a garden path with your bobbing duckies all nodding in agreement.

You may do what you please MH,but as you only made this !death spike! discovery (that you didnt know existed until i showed some test results),it is clear that you do not really know all that is going on within the circuit.

Your "red dot" current flow speculation is incomplete for starters, and wrong.  If you are going to show current flow you have to show a complete loop of current.  The blue dots are correct like you speculated, with the exception of the blue dots that lead to the LED and then stop and go nowhere.

Im not going down this babying road with you MH. If you cannot work out where the current flow continues from where the marked dot's are,then you clearly do not belong here.

Like I said before the Joule Thief transformer is temporarily shorting itself out and burning off energy and stealing that energy away from the LED.  This whole time your Joule Thief has been crippled.

In fact it is not.
The biggest waste of energy is actually in your 1k ohm resistor.
My testing today has confirmed this,and it also confirms my statements about being able to reduce the base resistance as the supply voltage drop's,that enables us to keep the LEDs light output at a constant(or near to)brightness.
Turns out that what i said is correct,in that the current flow in  L2 dose actually add to the the current flow in L1 during the off period,and this is what is causing the LED to go brighter when the base resistance drop's.
So you see MH,the 1k ohm base resistor is actually dissipating power that could be otherwise used to drive the LED.

When you get the reverse current flow that is an energy burn where energy is burnt off in the N-P collector-base junction and also in the base resistor.  So no go for a mechanism for making the LED brighter.

A contradiction on your behalf MH.
You clearly state that energy is being burned off in the base resistor--i say the same,and once that base resistance is removed,then that energy is added to the energy of L1,and sent to the LED.

As I previously stated when you lower the base resistance, it's really a secondary effect that makes the LED brighter.  If we assume that for both a 1k base resistance and a 5000-ohm base resistance that the "fully ON" (a.k.a. "hard ON") then the rise in current through L1 when the transistor switches on is identical.  However there is a secondary effect that makes the time period when the transistor remains on slightly longer, and that allows for a smidgen of increased current to flow through the L1 which results in an LED which is a smidgen brighter.

Partly correct,but only while the battery is still reasonably healthy. As the battery voltage reduces to around .8 volts(in my test setup),the secondary effect is from the current flow in L2.
As battery voltage drop's,the frequency rises,but as we reduce the base resistance,that frequency can be reduced,and the light output maintained--even though the P/in is now less.

N

ow, we can't forget that your Joule Thief is not functioning properly.

My JT is functioning correctly. It functions the very same way the other two i constructed-with only very minor differences due to things like number of turns of each coil,and the size of the toroid core.
All three have the very same operational  characteristics,and near identical scope traces.

So it would be worthwhile to repeat the variable base resistor tests after the problem has been fixed and see what the results are.  I am going to suspect we will see something similar with the LED slightly increasing in brightness for the same reasons.  And of course when the problem is fixed presumably the LED will be brighter overall.

There is no problem with the way the circuit is operating,nor the other ones i built today.
In fact,i will be presenting a JT circuit that is most efficient based around this !now found! reverse current flow.


Brad