Joule Thief

[resonanceman]

Hello Gary,

I have tried to plug leds on the back end of the JT to find and or detect the back emf. What is the best way to do this? I cant seem to find a way to get it to work? I have plugged a led from the base to the negative post of the battery and it showed no spikes.

However I can read 4.5v on my Scope on the negative of the battery?

Any help would be a blessing,

Thank you.

-Altrez

Altrez

On   basic JT circuit  the LED is connected between the  collector and the emitter  of the  transistor

Try  it in  both  directions....... it  should only light iin one  direction


You might  try  adding  another winding   if  you have room on your  toroid
You  you  said  you  had 4.5 V  on  your  battery.
I would  try  adding another winding  with  around the same number of  turns as your primary.......    then  measure  across the ends of that winding.......   quite a few  JTs will light  a LED in either  direction on the secondary.........but one direction  is usually much  brighter.

ANother  thing to  try.
Most of the  instructions for beginers  that I have seen  tell you to use a resistor  on the base of the  transistor.......I  strongly suggest a pot ......a variable resistor .......  It is wise  to check the full range of the pot  each time you change ANYTHING on your JT

ANother  thing  you might  try is  adding  a capacitor across  your resistor  or pot .......this makes  a tank circuit.    I would  start  with a .1uF .......  I  try  several different sizes   of cap  on  each JT I make.,
Some coils  will not  run without  a tank circuit....... I am pretty  sure  that this is not the case with  your  coil..........because  you got 4.5 V already

gary

Edit

The picture shows a basic JT
The red circle  indicates where the LED goes
The blue circle shows the tank\
The green squiggle is suposed to be an arrow indicating a variable resistor

[altrez]

Altrez

On   basic JT circuit  the LED is connected between the  collector and the emitter  of the  transistor

Try  it in  both  directions....... it  should only light iin one  direction


You might  try  adding  another winding   if  you have room on your  toroid
You  you  said  you  had 4.5 V  on  your  battery.
I would  try  adding another winding  with  around the same number of  turns as your primary.......    then  measure  across the ends of that winding.......   quite a few  JTs will light  a LED in either  direction on the secondary.........but one direction  is usually much  brighter.

ANother  thing to  try.
Most of the  instructions for beginers  that I have seen  tell you to use a resistor  on the base of the  transistor.......I  strongly suggest a pot ......a variable resistor .......  It is wise  to check the full range of the pot  each time you change ANYTHING on your JT

ANother  thing  you might  try is  adding  a capacitor across  your resistor  or pot .......this makes  a tank circuit.    I would  start  with a .1uF .......  I  try  several different sizes   of cap  on  each JT I make.,
Some coils  will not  run without  a tank circuit....... I am pretty  sure  that this is not the case with  your  coil..........because  you got 4.5 V already

gary

Edit

The picture shows a basic JT
The red circle  indicates where the LED goes
The blue circle shows the tank\
The green squiggle is suposed to be an arrow indicating a variable resistor

Hey Gary,

Yes I know how the basic JT works I have made a bunch of them. I have added up to 12 secondary coils on one toroid  and can easily light several 100 LEDS.

I always remove the led on the basic JT and just use secondary's. I have a tank circuity with an adjustable cap that I added 12 months ago and I am also using a pot and have for a very long time.

I guess what I do not understand is how you are detecting back emf? I can hook up a 1.2 volt battery and place a cap in parallel with it then fill a 12 volt electrolytic cap to 4.5 volts so I know that there is "something happening"

Just trying to understand the back emf stuff.

Thanks!

-Altrez

[sirmikey1]

Altrez,
   As far as discernment....   When you short the hot to ground, you get a spark, and that's your spike, extreme amplification, called negative entropy.   The way I see it, and I may need correction, is that the transistor B & E work as diode, and are being shorted, hot to ground, with every oscillation, spikes.  That's what makes the JT a Thief, gooses or bumps/pumps the battery. 
   Has anyone here worked with visual spikes, to mod? 
Mike

[altrez]

Altrez,
   As far as discernment....   When you short the hot to ground, you get a spark, and that's your spike, extreme amplification, called negative entropy.   The way I see it, and I may need correction, is that the transistor B & E work as diode, and are being shorted, hot to ground, with every oscillation, spikes.  That's what makes the JT a Thief, gooses or bumps/pumps the battery. 
   Has anyone here worked with visual spikes, to mod? 
Mike

Hey Mike,

Thanks for all the help. I thought the reason the JT worked was because it took the low voltage from the battery to run a transistor. that when hooked to a toroid amplified the voltage and power the led and or whatever else runs off stepped up voltage.

I have seen some big spikes on my scope from the secondary's and they look very interesting. But what I find is really interesting is when the JT is tuned a certin way you can fill a cap that is connected in parallel to the main 1.2 volt battery.

So i think that if you where to place say a 10F cap in parallel with the battery you could remove the main 1.2 battery when the cap was full and then run from the cap alone.

This was the first part of my self runner I posted many months ago! I just never got a chance to figure out where the spikes where coming from?

Thanks!

-Altrez 

[sirmikey1]

Altrez,
  Again, correct me if I"m wrong.   
M