Joule Thief 101

[resonanceman]

I do not have much time for adding  stuff here at the moment .
I thought  if  others here are like me they probably  will  be courious  about  kinds of things  you can make a JT with .

I thought  I would  post a few pictures  of some of the JTs I have made .
Maybe   one of  these pictures will give someone an idea .

The first is  made  from the  around 150 ft of cat 5  cable
I used one  pair  as a primary  the  other  pairs  as a secondary .

The  light  is  a LED array that I got out of  a LED floodlight
The box  said  it used 5 W  and replaces a 45 W floodlight .
I use   this kind  of  array alot .


gary

[resonanceman]

The  first picture is  a JT  coil made  with  the core of a flyback   transformer .
Notice  that the  primarys  The  white and  blue wires  are in the  MK2 style
3 wraps of each  wire on each end of the  core.

More on  styles of primarys later .


The  second and third  are of  an experment  with feeback and flyback.
I am lighting  a 25 W CFL  and  a 90 LED array . 
The  coil  above  is powering these lights .
Changing  one  wire  changed the balance of the circuit  causing a shift in  where most of the power  was  going .

gary

[jeanna]

Hey great topic!

Could somebody say something in regards to the wire gauge and turn count on primaries and secondaries?

Is it better to have a thicker wire gauge with fewer turns on the primary and thinner wire with more turns on the secondaries?

How might proportion affect efficiency?

Does it matter how tight or loose the wire is wrapped?

Hi sierraloewe,
After you have made your first jt and it works, then it is time to delve into those questions.

Follow the makezine or evilmadscientist youtube as closely as you can.

The gauge I use for the primary bifilar is 24awg. I got this from a telephone extension cord.
The length you will need to make this first one will be about 14 inches of each wire.
This depends on the fatness and diameter of your toroid, so this is just a guess. (I use a small one and it takes 11 inches of each wire and is very generous.)

After you have made a plain joule thief make a second one exactly the same way. Put the led into the led spot but do not solder it.
Remove the led when you prove that the circuit works.
Now, wind a secondary.
The choice of gauge for the secondary is up to you.
The thinner wire will make higher voltage, but the problem with really thin wire (like 30awg from radio shack) is the insulation is easily scratched. If it gets scratched you will have little to no voltage from your output.
One more thing about the secondary.
The side of the primary that connects to the collector coil is the part that is being "transformed" so, if you have 10 turns on the collector side (you do now if you are following the makezine video) Then double that will be 20. So, make your first secondary with 20 turns.
This will give you a starting point for reference voltages.

Now, you have 2 very useful circuits.
1-the plain jt is the best way to get the last bit of joules out of the battery. It makes a terrific emergency light.
2- The battery needs to be a little higher for the secondary to work. There are exceptions to this, but most of the ones that use a secondary run down after the battery is at about 1.1v.
So, you use the jt with secondary then when it is no longer bright you switch that battery to the plain jt.
This does not apply to a rechargeable battery.
Do not use a rechargeable in a plain jt, because it is not good for batteries to be so thoroughly drained.
(I could never figure out why but it seems to be so.)

After you have made these 2 you can start experimenting.

I have found that it is very important to make the wires wound snugly onto the toroid.
It is possible to have a good one that is loosely wound but if you want high voltage... get it tight around and try to have as many winds as you can actually in contact with the ferrite.

(I believe there is a difference in opinion about loosely wound together, but this is not about wound together, this is about being tightly wound on the toroid itself.)

That toroid is a powerful source of "something" that makes high volts.

I hope this helps.

jeanna

[resonanceman]

Here is one  with made  with a  complete  flyback transformer .

Just map out   the continuity  and the  resistance of the  coil   Then  choose your  windings .

[resonanceman]

There is  a MOT  ( microwave over  transformer )  as a JT

This is  using  1.5 V
I have not  tried  this  with 12 V yet