Joule Thief

[gadgetmall]

I have found that without some sort of L or C  that is takes a low resistance load to "fire" a high resistance load . ie put an incandescent bulb momentarily  across an led bulb . this is at a lower input voltage below 5 VCD,


Congrats on the finest bunch of Mods anywhere !

i am not worthy of moderation and can have moments of insanity


Thank you Stephan and Great Choices !

gadget
Gadget

[hartiberlin]

Hi Groundloop,
many thanks.
I will try to hook another transistor to the base of the MJE1100 so I will
have a 3 transistor Darlington...
I still have a few smaller NPN transistors here...

Well, does anybody know,
where Laserhacker does connect this graetz brdige rectifier in his new video ?

It is very hard to see in the video as he pans back and forth....


Also I had seen 2 videos from a guy on youtube, where he just used 2 different metals to power some kind
of Joule Thief...
In his second video he used his window metal  frame and a ground rod outside...

But I don´t find this video anymore...
He did not use a battery at all and he said, he could power his coil this way....
He was using a transistor to switch it and looked simular to a Joule Thief circuit...

DOes anybody still find this video on YOutube ?

Many thanks.

Regards, Stefan.

[Groundloop]

Hi GL,
can you or anybody else tell me, why in a DC circuit to test the Darlington transistor
a Darlington MJE1100 is not able to switch a load,
if one touches with the base the positive 12 Volt supply voltage ( e.g. from a battery) and just switches
an incandescent 12 Volt lamp at the collector (emitter is at ground and the lamp is from collector to plus pole of the battery)

Very strange !

It only works to switch the light on when I connect the collector to the basis !

Very strange.. Is my MJE1100 defective ?

Was the same with the BDV66B, although it is PNP  when I used the reversed supply polarity...

Somehow the Darlingtons seem to work differently than normal transistors...

I thought they would just have higher current amplifications ??

Stefan,

Are you sure you get the pins correct on the MJE1100?

Se attached pinout.

GL.

[hartiberlin]

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.

[TinselKoala]

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.....