Joule Thief

[resonanceman]

@ Gary (resonanceman) and all other experimenters who have experience with a lot of different "cores", toroids or "transformers" in a Joule Thief circuit:

Gary, what is your experience with "screeching" or "singing" of cores, toroids, wires or transformers?

This happens in the 1 to 50 KHz range of oscillation. Also lower harmonics of the Joule Thief frequency happen and are sometimes in the hearing range of people and pets.

I am in the process of doing a series of measurements with different air core coils in a Joule Thief circuit.

At the moment I can light 10 to 30 LEDs with a frequency of 50 to 150 KHz (from a 1 Volt power source). Best so far is an air core with a diameter of about 110 mm, 20/20 bifilar L1/L2 and a 200 turn secondary (standard Joule Thief circuit with a 500 Ohm resistor on the base of the transistor).

The big problem is high Voltage (e.g. 1200 Volt) from a 1 Volt power source. Even with air core coils I can not reach high frequencies. I am kind of stuck with 20 KHz (which are bothering people with good hearing and pets). With an air core the noises made are very faint, but they are still there. With toroids the noises are rather strong. With toroids (and high voltages on a secondary L3) I am stuck in the 4 to 6 KHz range.

All seems to be good once the circuit swings with more than a 100 KHz.

It is easier to reach higher frequencies when starting with a higher Voltage (e.g. 4 Volt or 6 Volt), but one has to be careful not to overheat the transistor or the base-resistor.

I "see progress" with bigger diameter air coils (200 to 300 mm). The bigger coils show very nice regular patterns when swinging, not spikes like toroids or transformers.

Attached see one example with an 110 mm diameter air core. The big bumps are happening with 108 KHz.

When I put a 3 K resistor on the base (with a 1 Volt power source) I can create nice sine waves with several hundred KHz on a secondary L3, but the voltage stays very low (e.g. 60 Volt) in spite of the many turns of L3 (see second scope shot).

I also want to go into pancake type windings for L2.

The "trigger L1" (going to the base of the transistor) should have fewer turns to increase frequency (e.g. 5 turns). So far "high frequency" has lowered very much the voltage on a secondary L3 no matter what I do.

Greetings, Conrad

Conrad

you  can read  a little about what I believe the cause of  the high pitched noise is here.

http://en.wikipedia.org/wiki/Magnetostriction

I agree that potting the  coil in hot glue is probably the best answer.........Hot glue is  soft enough to absorb some of the vibration....a harder material might just transmit  the vibration to the surface.

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Many  of  my JTs  are made for 12V
I found same  1.8K ohm power resistors in an old monitor .......I  put one of those on  on the wire  just  before my potentiometer. ( pot )
I could  run 12V  with  a much lower resistance but I like my circuits to run cool.

When I  started  using 12V I switched to  2n3055  transistors.   Now I  use TIP3055  I find they take more abuse........
I always use a heatsink........ with TIP3055s  I just use  a piece of aluminum from the hardware store..

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you talk  about making sine waves........ I  think something most  people that have visited this thread have missed is that JTs  make impulses.........spikes
Learning to use these impulses  for practical things is  half the fun.......
The impulses  are like  a different kind of  electricity ...... they follow  many of the rules..........but not all of the rules.
I have been playing  with JTs for a few years now....... I have not   yet  done more than to scratch the surface.........the more I do........the more I  come up with new theories and  projects
Right now..........if I  could spend all my time  playing  with JTs and  had  unlimited money........I could probably stay busy a few years.

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I do not have a scope........so I have  no way to check the frequency.
I have noticed that a capacitor across the base resistor  can change the frequency..... it also seems to me that the circuit pumps more  power  with each cycle  when you use a large cap.
With some of my JTs  using  a large cap........ (like 10uF ) I can  get my 90 LED array to blink  once every few seconds.


gary

[jeanna]

ty i will take a look at them i belive i found an inducter in the cfl light it has the markings 472k

In short,
You have 3 inductors in your jtc.
the first 2 are the center tapped primary and the third is the secondary pick up. In yours with a second secondary, you have a total of 4 inductors.

Depending on the permeability of your toroid, your inductors will give you more or less henries. (a henry is the way the inductor is measured.)

I hope this clears that up.
I am sorry to confuse.
btw, that guy Lewin is the tops. He is great.

I need to go for the evening. bye,

jeanna

[dasimpson]

i have to point something out i just read on page 310 about bridge rectifires is does matter what pins the ac voltage goes to ac must got the the markings~ ~ if they got to any other it will not be a full bridge rectifire but a half bridge meaning with ac you would only get the + side of 0 not the - side of the ac
with a full bridge rectifire it take the - side of 0 and the + side of 0 and forced them out the + side of the rectifire to get the wave to + 0 all the time on a scope the dc will look like loads of hump back bridges and always stay aboove the 0 line ac will go above and below the 0

ac is safer then dc as it drops below 0 means you can let go dc is not as safe once you touch dc you normaly can not let go as it will lock your muscles solid this is as the right voltage and ampage mind you

the bit i dont get is why a bridge rectifire has any affect on dc pulses unless the jt really is producing ac voltage so if that is the case most inverter will have a jt of some sort

another thing to point out ac in a house the neutral dose go to earth on every pilone over so many miles
think abaout this ac is pulses of electricity but they move back and forth now for there to be a hot wire and a cold(nueatral) one must go to earth otherwise both terminals would be hot (live) if you done belive this go look at some pilones you will see some have shorting rods i was told this info by a mains distributer engineer aka my step dad

[dasimpson]

may i ask what this is

NOT TO CONFUSE ...

but to clarifly .... 

i drew!!


here ya go

take it or leave it    lol 

ist!

369 

[the_big_m_in_ok]

may i ask what this is

http://www.overunity.com/index.php?topic=6123.msg169507;topicseen#msg169507

The post above is on pg. 311,  Reply #4663 of the "Jule Thief" thread.

If you read more of ist's posts and try to understand what his work is about, that might help to understand him better.

Then, again, ist is ist.
But, he does have more than a little experience in electronic bench experimentation and I've found his suggestions helpful in high voltage electronic engineering.

--Lee