Joule Thief 101

[tinman]

Here's something else to consider. In the standard JT, the toroidal windings actually form one continuous winding in the same direction, with a center tap. You can save yourselves a lot of trouble by simply taking one strand of wire, winding the toroid or ferrite rod etc. with one continuous single-layer, connecting the ends to Collector and Base resistor/capacitor (if used). Then use sandpaper to remove the insulation of the magnet wire in a "stripe" along the outside of the toroid or along the length of the rod, and locate the tap (which goes to positive rail) in the best place by experimenting with connecting to the uninsulated stripe. Once you have found the correct ratio location, solder the "center" tap to the bare stripe at that spot. This is similar to the way that a traditional inductively-tuned crystal set has taps located along the coil for tuning to particular stations.

A good idea TK.
To add a bit to that,we could use a wiper as they do in variac's,and have the positive of the battery hooked to the wiper. This way we can make the adjustments on the fly.


Brad

[tinman]

 author=MileHigh link=topic=8341.msg478230#msg478230 date=1458778346]

Your pitch about currents through L1 and L2 adding up to put more magnetic energy into the core is dead wrong.  See my earlier posting.

Your earlier posting is wrong-along with the statement above.

It's pretty obvious this time that reducing the base resistance barely increases the intensity of the LED and it can only be picked up by the light meter.  Changing the base resistance makes no change in the LED intensity for the naked eye.

And how could you have possibly seen the LED change in brightness when it was under the light meters sensor?

For the 10-ohm CVR setup, you are looking at a massive anomaly where the L1 coil is discharging straight into the L2 coil via the 1k resistor and sucking some life out of your Joule Thief and you are not saying anything about it.

You are  lost.
You simply cannot add everything up,and this is your downfall.

-

For the 10-ohm CVR setup, you can see that lowering the base resistance gives you more current through the base-emitter diode of the transistor.  The assumption is that this is excessive current that is doing nothing for you except wasting energy, just like I have said several times.

Your still lost 
What happens to the current flowing through L2 when the base current is increased ?.
What happens when the current flowing through L2 increases?.

I don't believe that putting a current limit on your bench power supply will emulate a nearly discharged battery's output impedance.  I would think that you should measure the actual output impedance of a nearly discharged battery of a given size and chemistry type, and then simply put the appropriate resistor in series with your bench power supply.

As i said to Mag's a few post back,i have already done this,and i recommended this to him as a test setup. The results were the same as in the video of course.

So, the variable base resistor is not doing much good at all for you in this clip, and then there is the discovery of the massive anomaly in your clip.  I have a few more minutes to watch to see if you have anything to say about it.

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.

[tinman]

Well Brad, you have a new elephant in the room, I am calling it the "Joule Thief death spike."  See attached.

How could you not say anything about this?  It's truly mind blowing when you get these absences of reaction when something truly unusual happens.  You have this huge spike of reverse current going through the base of the transistor and you say NOTHING?  LOL   Like a bloody lighting bolt it goes right up L2!  You are the Dr. Frankenstein of Joule Thieves!  LOL

Cat's got your tongue?  Zap the cat with a lightning bolt of current!

Lol
!!!!huge!!!! spike you say lol
Did you look at the VPD setting on CH2 MH ?-and how narrow the time period is for the !!!huge!!! spike lol.
lets not talk about junction capacitance--we all know you hate that subject,and that it may provide some proof of the miller capacitance effect being the cause of the cool joule being able to operate without any inductive coupling between L1 and L2.
It's all coming back now to bite you on the ass--and you are the one showing your own errors lol.

I love it when a plan come together

Brad

[MileHigh]

Lol
!!!!huge!!!! spike you say lol
Did you look at the VPD setting on CH2 MH ?-and how narrow the time period is for the !!!huge!!! spike lol.
lets not talk about junction capacitance--we all know you hate that subject,and that it may provide some proof of the miller capacitance effect being the cause of the cool joule being able to operate without any inductive coupling between L1 and L2.
It's all coming back now to bite you on the ass--and you are the one showing your own errors lol.

I love it when a plan come together

Brad

Junction capacitance my ass.  You should consider that the "bad old days" where you throw words against a wall like spaghetti and hope that they will stick.  How does a Cool Joule work?  Answer "Miller capacitance effect" is a total FAIL.

What's biting you in the ass right now is that there is a major problem with your Joule Thief.  So you can clown around in a daze or undertake to investigate it and fix it.  It looks like it may be seriously compromising the efficiency of your Joule Thief and could be damaging to your Joule Thief.

I don't recall Magluvin doing any current traces for the base input.  You have a problem, so do you dance around like a clown or figure out how to fix it?

[MileHigh]

Your earlier posting is wrong-along with the statement above.

Go ahead and do a timing diagram and demonstrate how the magnetic energy in the core increases when you have current flowing through L2.  Show how this supposedly makes the LED brighter.  Don't just rattle off a spur-of-the-moment "explanation" - roll up your shirtsleeves, pick up a pencil, draw out a timing diagram and try to prove that you are right.