Joule Thief

[hartiberlin]

P.S: I have the same circuit as this now:
http://www.overunity.com/6123/jule-thief/dlattach/attach/117923/

but I have a 25 K linear Pot instead of the 10 K Pot and instead of the power supply
I have a 15.000 uF cap and I also have a 5.6 K resistor going from the mid tap of the pot to
the base.

Instead of the 2N2222 I have a BD 139 and instead of the 2N3055 I have a MJE1100.

I also have a transformer with Metglas or iron tape core ( don´t know, bought cheaply
from an electronics store...)
with the primary having about 15 turns and the secondary having 100 turns.
I have a 230 Volts AC 3 Watts LED bulb.

Hope this helps.

Regards, Stefan.

[hartiberlin]

P.S: Tommorow I will use my scope to see, what is going on...

Regards, Stefan.

[Groundloop]

Hi GL,
is the upper left picture a top view or a bottom view ?

Yes, that was the problem with the MJE1100 datasheet !

Now I have got a MJE1100 and a BD139 connected as a new
Darlington pair and got my LED bulb running on the cap,
but I don´t get this blinking effect.

I can only get it to light up , when I permantly connect the 12 Volts supply via my 15000 uF cap.

Still have a 25 K pot across this cap and a 5.6 KOhm resistor going to the base of the new darlington
to tune the base potential....

ALso I don´t know, where Laserhacker put his graetz bridge to...


Have to leave the house now.... Will experiment tommorow further on,
when we know, where Laserhacker did connect his rectifier bridge...

Regards, Stefan.

Stefan,

Normally all data sheets display the transistor top view.

GL.

[hartiberlin]

Stefan,

Normally all data sheets display the transistor top view.

GL.

Yes, but I also had some problems with nonworking croco cables and contact problems...

Never work with these awfull crococables... but I now don´t find my wood plank, where I wanted to
use nails to solder it all on...

Have to go...

Hopefully Laserhacker will be still around today and will tell use the new exact circuit diagramm
with screwing it up again 2 times ! Lol !

Regards, Stefan.

[Groundloop]

Wow.... I fell behind there, got a lot of catching up to do, I can tell..... but meanwhile....

@GL: If you want more output voltage you need more inductance I think. The total inductance of both coils (or coil segments) is the key, I think. The voltage spikes on the output come from the collapse of the field in the inductor(s), so you get more voltage in two ways: increase current for more field -- this is done by raising the input voltage, not what we want necessarily, or increase inductance for more field in the inductor, by adding windings or using different core materials.
If both coils are wound on a single core like most of us are using (but not Sohei Thoth, very nice work there) then changing the core will affect both coils, obviously, or the inductances can be varied separately by varying the number of turns.
My best HVJT uses a 10mH inductor from an old TV set, looks like about 300 turns on a cylinder of good ferrite, and I wound 30 turns of heavier wire on top of that for a "primary". It makes well over 600 volts no-load on a "dead" AAA input,  and can charge up external caps very quickly thru a diode rectifier.
I have not yet sorted whether or not it is the primary inductance or the secondary inductance separately that is more important for HV.

OK, back to catching up.....

TK,

I understand what you are saying. That was also my conclusion.
But there is more to this circuit. I recommend that you build it and test it.
It is a fun circuit to play with and probably a very useful circuit when we want
to power LED lamps from batteries. I did try some ceramic capacitors over
the output and the light in the LED bulb did increase. Also the LED brightness
goes down when I connect an antenna to the collector of the power NPN.
Need to test more on this later on.

GL.