Joule Thief

[resonanceman]

good question, hard to answere.

tuning is an art.
it is much like troubleshooting.

the thing is hard because multiple parameters are at play.
i will only write about the more important ones for the jt.

adding a pickup with a load will change the natural bjt's frequency.
changing the base's resistor value can fix that most of the time, but not always.
adding a RC to the transistor base, a capacitor in parallel with your potetiometer, might be required.
capacitor and resistance value can vary

cores(toroid) can be made from various material.
some have low coeficient of coupling(ferrite, best at higher frequencies), some have high coeficient of coupling(iron, best at lower frequencies)
higher here does not nescessarly mean mHz and lower does not mean 60 Hz either.

to fix poor coeficient of coupling you can do 2 things :
get the transistor to work at an higher frequency. <- most effective on some materials
or add turns to your bjt's base and/or collector coil.
sometimes both methods are required.
spreding the turns around the toroid can help too, but never forget that the mag field is at 90 degree to the wire creating it.
wire at \ and at | does not make exactly the same effect on the core.

the first thing you must do is to find what problem(s) your core have.
too low frequency ?
poor coupling ?
both ?

i hope this will help everyone.

Thanks  The NOP

I don't  know  that  my toroid  has  any problems .......I used it  because  I  have had my best  success so far with  this  kind of toroid .
( goldmine  5 fir $1  )   
I always  start out  with  a  good sized  cap  across the   pot
I have found  that some  will  work  without the cap but not all of them  ......but  so far they have all worked  with a cap .....so   I use one  to get first light

spreding the turns around the toroid can help too, but never forget that the mag field is at 90 degree to the wire creating it.
wire at \ and at | does not make exactly the same effect on the core.

This  does not  agree with what I have been finding
At  first  I started   spreading the   windings  around the  toroid ......the idea was to  cut down on dead  spots.
I think  the  design  of the MK2  eliminates most of the  dead  spots .
I have notices that  squeezing  the  windings  close together  usually helps  more than   winding them  tightly on the toroid .
Because  the  primary  windings  are single layer ..... I have been  placing  a string  across  the  outside of the toroid where the windings will  be ....... and I  tie the windings together  once I am  finished 

gary   

[jeanna]

@Gary,

Mine  looks  just like this   except   the  picture shows 3 windings on each   leg ......mine has 10 .
Just in case I did   do something  different  than  the  rest of  you ..... I connected   it  by   hooking  the  leads  on the l left  side of the  picture together and  plugged them into  B+.

So far so good.   

The  wires  on the  right side of the  picture  connect to my pot and  my transistor .

You mean connects to the pot the other one to the collector , I am sure. So, yes.

A  cap  across the pot  didn't  seem to help  anything

Me either.

I think you are starting with too many turns.
MK1 indicates that he uses only a few.
Your tuning will tell, but expect it to be more like a total of 7 of each color total.
That would be 7T,7T primary.

Gary, do yourself a favor and just wind one even temporarily like the MK1.
You can take it out and do the other as you suggest.

When you wind the MKx secondary you go up then down on one side of this.
I don't think you need to cut but leave some wire when you cross over and then go up then down again.
That is an MK1 It is really powerful.

thanks,

jeanna

PS

I somehow missed that picture. I thought I had been through all the pages of this thread at least 3 times.

I have never seen that one!
I have not made mine like this, but I will.
Mine are made with red on one side connected through the middle to the other color on the other side. This way looks like it won't want to un-wrap as much. That is what I didn't like about the split method.

Do you happen to know what page or date that is from? or, did MK1 post it?

[altrez]

Hello All,

I just wanted to take a second and say that I am so very impressed with everyone's hard work. I have ordered 5 new toroid's from CWS. I plan to start testing them in the next week, I also ordered a new scope and a LCR meter.

I think that I am very close to powering a cfl from my current setup my goal in the next two weeks is to power a 15inch tube!

Take Care,

-Altrez

[Cap-Z-ro]

" I thought I had been through all the pages of this thread at least 3 times. "

Jeanna.......no wonder you were able to locate the tri-axis toroid so fast!

Still impressive nonetheless though.

By the way I may have missed it because it hasn't occurred to me until now, has anyone tried different sizes of wire between the primary and the secondary ?

Regards...

[gadgetmall]

Gadget   do you have a  part number?

It sounds like   something I would like to play with


gary 

Hi Gary yes part numbers are ALD110800/ALD110900. They are available from Digikey as quad and dual devices in PDIP and SOIC packages in four different models and they feature, as the most salient specification, Gate Threshold Voltage of 0.0 V +/- 0.01V @ 1 uA. A Matched pair can "Flip Flop" for free ....

Gadget