Joule Thief

[TheNOP]

I even found a link , http://www.tesla-coil-builder.com/bifilar_electromagnet.htm

don't beleive everything on internet without confirming from a more credible source.

that test from the link is a "guesstimate" experiment.
i have been fooled by a site like this one a few years ago...
real tests require a Gaussmeter(DC) and/or a magnetometers(AC).

[electricme]

@Xee2 and The NOP
There is an implication in this forum that I am incorrect in suggesting that current limiting resistors should not be used if transistors are paralleled up, to get the enth degree of energy out of their circuits.
However, I again supply further evidence that the correct way is the one I have suggested.
If others want to do it "their way" so be it.

adding resistors at the transistors emitters is the way to limit current.
but..., is it what we want to do ?
for me, it is not the way i want to limit it.

the way i would try it is: a trim pot on each base + one potentiometer connected to all the trim pots.
once the trim pots are correctly set, all transistors will work equally.

OK, looking back through this thread you will find reference made to using a 1 ohm resistor to measure current flow, this same resistor is used for self regulation of the current flowing through parallel transistors.
But none raised any remarks about any loss caused by this at the time.

.47 ohm resistors would be preferred for the Joule Thief if paralleling up transistors.

If TheNOP wants to add resistors to bases of each transistor, OK, but you will find you will be constantly adjusting these settings as the transistor output drifts up or down with temperature changes, resulting to current changers.
The resistor can restore equilibrium automatically.

The more current drawn from a device will also have a rise in temperature.


Here is another reference to why 1 ohm resistors are used in emitter outputs.
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=61230

or try here, in this circuit there are 18 Transistors sharing the current, via current limiting resistors, each is .47 of an ohm at 20 Watts each.
http://www.electro-tech-online.com/attachments/general-electronics-chat/9515d1158115560-transistors-parrallel-increase-collector-current-1.5kw-amplifier.png

This power supply circuit below has a number of TIP2955 transistors, all their collectors have matching current limiting resistors.
http://www.mitedu.freeserve.co.uk/Circuits/Power/1230psu.htm

If you don't want to use the above technique, then get a couple of CMOS transistors, they don't require resistors on emitter legs, but these are more expensive.

jim

[Mk1]

Double Post sorry !

[Mk1]

don't beleive everything on internet without confirming from a more credible source.

that test from the link is a "guesstimate" experiment.
i have been fooled by a site like this one a few years ago...
real tests require a Gaussmeter(DC) and/or a magnetometers(AC).

Well thank man , thank good you are there to keep us down, i would suggest having some suggestion from time to time , in the middle of all that Nop saying.

I made the test i work for me and Tesla , well , that site is fine !

You got fouled once is that why you always say nope.

Mark

[jeanna]

Hi Bill,

I am glad to hear you are around. I was beginning to wonder if you swirled away!

@ Jeanna:

I do not understand why you keep saying you want to begin an AC topic when everything I am doing is AC. (JT, EB, Fuji, etc.)  Feel free to do what you want but unless folks are using diode bridges on their JT's they are all AC anyway.

But most folks ARE using diodes and turning the ac into a single direction.  This is a fine thing to do. I just find that when an ac idea comes up it is quickly buried by other things on the thread that are dc related.
(like the brilliant idea of charging a battery, for instance)

The thread is so big and only a few want to concentrate or even poke at how to keep the ac going as ac, I want to do that and it is a little cumbersome at the moment because pages and pages go by before the AC idea is addressed as AC.

AC is what we produce from the secondary.

The plan for the ac thread is to be only looking at what can be done from the AC once it has been made and not the dc potentials.

Our world has AC in wires in 2 forms 240V 50Hz and 120 v 60Hz.
As soon as an EE wants to take a small amount to do something he collects a little rectifies and that's it . It is a habit. And there is nothing wrong with it.

I want to explore multiple output circuits which all have one ac source. They would be parallel circuits maybe with inductors caps resistors little tanks etc instead of diodes and rectifiers and batteries or super caps.
I hardly know anything about such wonderfullness and I want to change that situation...

If many people here were actually interested in keeping the ac, then there would be more posts about it.

So, the short answer is:
It will be easier to find the relevant comments and to be able to follow the history of an idea when that idea goes in the direction of ac and stays ac.

It may not help me, or any others wanting to explore the jt as ac generator, but I hope it will.

I am certainly not wanting to offend anyone. I hope that is clear.

jeanna