Joule Thief

[jeanna]

Hi Pardon,

It is quite a nice drawing, in my opinion.

I will say it to you too. take out those leds from the bjt. They are only useful to make sure you have things connected right. I always use one, but then take it right out.

The special thing happens with the secondary/pick up.

Also, you have .92v at the no load. etc. What do you mean by that?
Are you meaning to say amps there?

It looks like a really good circuit. Just move those leds to a secondary. You will get very good light and at barely any amps cost. You will love it.

I can't codify it, xee can, but I usually get lots of bright lights when arranged in a parallel way.
In series is more problematic. It seems you need 3 to 5 additional wraps of the secondary for every new light you put in series.
I know that is not what I showed in january, but many since then have taken many turns for each additional light when put in series.

I am just trying to do something systematic with some of mine. I have a lot and sometimes the lights are bright with no draw and sometimes they are dim with a lot of draw. There are a lot of factors.

for instance, I was just checking something tonight and my eyes got blasted with 300millivolts!!!on the secondary as tested on the scope.

BTW what is the toroid you are using?

lots of questions, sorry,
what you have is a good jtc, though, after those lights are moved 

jeanna

[Pardon]

I found this so i thought i would post it here. i hope this may help out

THE TRANSFORMER
The secret of this circuit is the transformer.
We normally think of a transformer as a device with an input and output, with the voltage on the input and output being connected by a term called "turns ratio."
If the output has more turns than the input, the output voltage will be higher.  This is called a setup
transformer. If the output has less turns than the input, the output voltage will be lower.
This applies to "normal" transformers where the voltage is rising and falling at a regular rate, commonly called a "sinewave."

But the transformer in this circuit is different.
The voltage applied to it is not rising and falling smoothly, and thus it does not work in normal "transformer mode."
The voltage is being applied and then turned off. When the voltage is applied, the primary winding (the 90 turn winding) produces magnetic flux. When the voltage is turned off, the magnetic flux collapses and produces a VERY HIGH voltage (in the REVERSE DIRECTION), in all the windings.
Our transformer is really a coil in flyback mode with a feedback winding.
The feedback winding delivers a voltage to the transistor to turn it on HARDER. If the winding is connected around the wrong way, the circuit will not work.

The other important factor about the transformer is the core material. There are many different types of
ferrite. Ferrite is a type of iron which is powdered very finely so that the magnetic lines that pass through the particles do not create eddy-currents. These eddy currents absorb the magnetic flux.
The circuit also employs a term called RE-GENERATION. This is the effect where a circuit is turned on slightly by a component (the base resistor in this example) and then the transistor turns itself on more and more until it is fully turned on. The feedback winding is configured so that the voltage it produces (actually the current it produces) is fed into the base to turn the transistor on. Thus the feedback winding is very clever. It produces energy and is delivered in a particular direction - in
other words it can be a positive or negative energy. In this case it produces positive energy, to turn the
transistor on harder.
This is called POSITIVE FEEDBACK as it turns the transistor ON during the active part of the cycle.
Now we come to the MAIN, PRIMARY or FLYBACK winding. This winding produces a high voltage during part of the cycle (the FLYBACK part of the cycle) and this is passed to the LED.
If the LED is removed, the transformer produces a high voltage with a low current, but when the LED is
inserted, an amazing thing happens. The energy from the transformer is converted to a lower voltage with a higher current. What actually happens is the LED absorbs the energy and turns it to light as soon as the voltage rises to 3.6v. We could achieve the same low-voltage, high current requirement, with less turns, but the number of turns has to be determined so the core does not saturate.
The voltage for the LED is produced when the transistor is switched off and the magnetic flux in the ferrite core collapses. The speed of the collapse produces a very high voltage in the OPPOSITE DIRECTION and that's why a positive voltage emerges from the end connected to the LED. These two facts are important to remember. The other important fact is called "transformer action." This is the action of magnetic flux. When a voltage is applied to a winding of a transformer or a coil of wire, a current will flow and this will produce magnetic flux. If another winding is present, the magnetic flux will cut the turns of this extra coil and produce a voltage in it. However, there is a very important point to remember. The magnetic flux can be: EXPANDING, STATIONARY or CONTRACTING.
When the magnetic flux is expanding, a voltage will appear in the second winding mentioned above.
When the magnetic flux is stationary, NO VOLTAGE will appear in the second winding.
When the magnetic flux is contracting a voltage will appear in the second winding with REVERSE
POLARITY. The size (the amplitude or "value") of the reverse voltage will depend on the speed of the collapsing magnetic flux. If the flux collapses quickly, the amplitude will be very high.
That's how the transistor turns itself on and on until it is fully turned on. At this point the current flowing through the circuit is a maximum but the flux is not expanding so the base of the transistor does not see the high "turn-on" energy and thus the transistor suddenly turns off.
The magnetic flux collapses and the transistor sees a reverse voltage on the base to keep it turned off until the flux is fully collapsed. The current through the resistor enters the base to start the cycle again.
From this you will be able to see how the transistor and transformer work.

[electricme]

@Bill,
Thank you for the link to the YouTube address, I took a look at it, its pritty good.


@ Xee2 and Gadget,

ho ho ho, do I smell a competition or a challenge between you both, the first to get 100 LED's lit from the lowest voltage possible, in time for christmas?, nothing like a competition challenge to hone the electronic skills. Whats the prize? 

Lets make this interresting.
Now, do they have to be turned on all the time, or can they be made to work by being turned on and off so fast that the eye cannot see it happenning, or is there a limit of time they have to be lit, anything from 1 second, or 1 miinute or 10minutes or, for 1 hour.

@Gadget,
I'm having a field day, Bought my usual Silicon Chip magazine, inside for free was the Jaycar catalog, drool drool drool.
Christmas wish list time again lol

@all,
Inside the above mag is an article on a Micro Curent Adaptor, I havent read it yet, but from a quick look through, some of us here might be able to use it. This is a Kitt that one attatches to the DMM meter.

@Jeanna
You asked me about amps on a DMM, the above might be of use to you.

Puppy Linix, I went to the below address because I heard there was a program called Puppy Linix, but when I got there I was bamboozeled by it all.
What actual file would I need to download to install on my older laptop? I want to try this out.
http://www.siliconchip.com.au/cms/A_111196/article.html what do you think of this jeanna?

@all
Silicon Chip has some good stuff. Scroll down the page to see the LED current limiter
http://www.siliconchip.com.au/cms/A_30372/article.html  this could stop LEDs turning into fuses.

jim

[electricme]

@Pardon,

Thankyou for posting the explination on the whole operation of the Joule Thief, even this old fogie understood it, well I'll need to read it a couple of more times for it to be understood completly,   

Seriously, Pardon, it is the best way this has been explained that I have seen so far, thankyou 

jim

[hazens1]

hazens1:

Excellent job man!  Did you say this was from a single AA battery on your JT coils?  350 volts, now that is well within the Fuji territory some of us had been working in earlier.  To my knowledge, no one has achieved this much output on hand wound toroids here thus far so.....very, very great job!  I know one of Jeanna's goals was to reproduce our Fuji results using the regular JT type circuit and it appears you have now done so.

I know you said photos were forthcoming but can you please post a step by step, or schematic of your circuit as I know, myself included, other will want to replicate it.  I am very excited by this so again, great job and thanks for posting.

Bill

Here ya go. I was able to get 365 volts from a 1.3 volt 125ma input. More testing and such to come when I have time. The added Pickup coil is the Green wire mixed in with the original Pickup in Gold wire. All 26ga wire from www.gobrushless.com, it's called newbie wire since you can get the same gauge in 3 different colors