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Author Topic: Joule Thief 101  (Read 926837 times)

resonanceman

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Joule Thief 101
« on: November 23, 2009, 04:18:06 AM »
This  thread is intended  to be a place for  people to learn the basics of how to make a JT ( Joule Thief )  and  what can  be done with them .

This thread is not to be used for asking  questions or  casual  dialog .   This thread is to be kept short  and clean .  The  goal  is to pack  as much  knowledge into a few dozen pages .

With the  recent turn of events  and  the possibility  of  proving  OU new people are bound  to show up .      It is not reasonable  to expect them to read 1000 pages  before asking a questions .
It is also not reasonable  for  the new people to expect us  to drop everything and answer  the most  basic questions .........over and over .

The schematic  below  is  a basic JT
It is shown  using  a 2n3904  but  2n2222s  and many other  transistors  have a proven  track record .   

The schematic  shows  a 1K resistor going to the base of the  transistor   I recommend using a potentiometer   ( Pot ) in  place of the  resistor .  In  real  life it is  a good idea to  sweep the whole  range of the  pot  each time  you make a change in the circuit .

ALmost any toroid can be used .
Low permeability  toroids are easier, they require less turns of the primary .
By the way .......the  2 windings shown  in this drawing  are the JT primary . 

One  thing that  causes alot  of  confusion   with new people  are the dots  drawn  at the top and bottom of the  coils .
I do not know the technical name for them .   I call them marks.
When  you are winding  your  toroid  use something to mark  either the starting end or the finishing end of both wires ..   Magic marker,   nail  polish, paint ........anything to mark the end.

WInd both wires together   as if they  were one . Try  6 or 8 wraps at first .   A very high perm toroid may  need more, a low perm  toroid  will work with less.

When  you  are  donw winding   find  the marks you made on the ends of the wire.

You should  have  2 wires on each  side of the toroid .
One side  will be wires with marks.   The other side  will be wires with no marks.
Take   one of the wires with marks and connect it to  one of the other wires with no marks .

The  Positive  side of the battery  is connected to  the 2 wires you  just  connected together.

The end  of one of these coils  is connected  to the longer  lead on your LED.
The other  coil connects to your pot  which  then connects to the base of the  transistor.

You now have  one of  the 3 wires of the  transistor  connected.
Connect  the  one of the other  wires  on the transistor  to   the same  end of the coil that you connected  the long lead of the LED to  ( at the same spot )

Connect  the  short lead  on your LED  the 3rd wire on your transistor   and   the negative side of your battery together ....... If you did all this  right  , you now  have a working JT

I will leave the  technical  terms to others .   In  theory   you have to  have the  transistor  hooked up  properly ..... in real life it  works  either way . Just  make sure you get the  base  hooked up right . ( at least  with a 3904 and 2222 )





resonanceman

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Re: Joule Thief 101
« Reply #1 on: November 23, 2009, 04:41:06 AM »
This  schematic  shows the basic  JT  with  a capicitor ( cap )  added  across  the  resistor  to make   a simple  RC tank .   
I always  have  use a  tank when  first  trying  a new toroid .  Some  toroids  will work without  a tank .......some will not   
I have never seen  a toroid  that would  not  work  with a tank circuit in place .     I have seen quite a few that  stop when the cap is removed .
I usually  start  with  a 1uF cap  but  a .1 sometimes  is better .


Another thing added to the basic  JT in this  drawing is a secondary .
A  JT  by itself is a novelty .     
It is the secondary that  makes  the JT interesting.
What  can  you get done with it ?
How much  voltage can you make ?

There may  be  many  secondarys  on  a JT
The  secondarys   are always  closed loops in and of themselves.  There is no electical connection to the  primarys.
The primarys ( the original 2 windings of the JT )  are called primarys  because they  are  what makes the  JT work .   
The  secondarys are also called takeoffs .......because they are used to take off power.


gary

resonanceman

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Re: Joule Thief 101
« Reply #2 on: November 23, 2009, 04:55:10 AM »
I found these helpful

Pirate88179

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Re: Joule Thief 101
« Reply #3 on: November 23, 2009, 04:59:56 AM »
Gary:

Great topic!  And very timely too.  You boiled it all down to simple steps.  So now, no one can say they can't make a joule thief.

Great job!

Bill

xee2

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Re: Joule Thief 101
« Reply #4 on: November 23, 2009, 05:20:50 AM »
@ resonanceman

More recently, the "secondary coil" in the above diagram has also been called a "pickup coil" instead of a "secondary coil". Although both terms are used. This is because there can be more than one pickup coil used and it does not make sense to have several secondary coils.




xee2

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Re: Joule Thief 101
« Reply #5 on: November 23, 2009, 05:38:24 AM »
A common question is, "how can I make a Joule thief that lights a fluorescent tube"? Well, there are many ways. I think this is probably the simplest.


jeanna

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Re: Joule Thief 101
« Reply #6 on: November 23, 2009, 06:45:45 AM »
At this moment the only thing I want to add is this excellent picture made by makezine.
There is a pdf that you can download that goes along with their excellent video.
Of course it is the basic joule thief, not the kind most of us are now making but the first one everyone should make.

http://www.youtube.com/watch?v=gTAqGKt64WM
I say watch this 3 times. (5 minute video)
1- all through
2- return to 1:09 and watch till the jokes at the end. Really focus this time.
3- return again to 1:09 and as you watch it pause and try to predict what comes next, and start making it. You can keep it buffered while you make it too.

jeanna

In this pic you can clearly see that the 2 wires are different colors, and you are connecting the end of one of them to the beginning of the other.
I believe this is the mistake most often made by first jt makers, so watch carefully.

WattBuilder

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Re: Joule Thief 101
« Reply #7 on: November 23, 2009, 07:34:24 AM »
ALL,

Due to the different experience levels that one may have.
Those of you who are attempting to build this circuit or larger circuits.
Remember to take the time for    SAFETY FIRST !!!

Accidents due happen.
High voltage does KILL
Capacitors due EXPLODE

Make sure proper grounding is used.
Make sure your face is shielded if not at least your eyes.
It’s wise to have a buddy around just incase of emergency’s

Please take the time to research safety and there is no such thing as a stupid question when it comes to safety.    Just ask.

Finally, remember to have fun!!!    Your building a really cool circuit.   

Howard

sierraloewe

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Re: Joule Thief 101
« Reply #8 on: November 23, 2009, 09:17:53 AM »
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?

jadaro2600

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Re: Joule Thief 101
« Reply #9 on: November 23, 2009, 02:07:33 PM »
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?

Loosely wrapped wires will make the torroids sing.  Having a larger number of winding on the secondary will create a larger voltage, the ratio on the primaries should be, but is not limited to 1:1, remember though that the current through the primary going to the collecter will be greater than the primary going to the base and thus the waveform on the secondary will be slightly offset ( thus it is more like pulsed DC than 'trued' AC.  ( innovation_station has found ways around this )).
- - - -
Rationalized Schematics and Alternative Designs ( by me, these have been tested and do work ).

edit:

I was going to post more, but these should do for now. Currently I'm testing deviations of the circuit; though I lack super or ultra caps, I'll be writing up instructions of my own some time for the resistor-less circuits.

The images below are old, each representation of the winding should have a shared core ( as a line between them, more like in the original post ).  My software is limited to Linux..and thus the output is hard to perfect.
« Last Edit: November 23, 2009, 03:40:37 PM by jadaro2600 »

resonanceman

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Re: Joule Thief 101
« Reply #10 on: November 24, 2009, 02:22:07 AM »
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

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Re: Joule Thief 101
« Reply #11 on: November 24, 2009, 02:40:44 AM »
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

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Re: Joule Thief 101
« Reply #12 on: November 24, 2009, 03:01:42 AM »
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

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Re: Joule Thief 101
« Reply #13 on: November 24, 2009, 03:34:28 AM »
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

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Re: Joule Thief 101
« Reply #14 on: November 24, 2009, 03:42:49 AM »
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