What is the mystery behind "white light led light from 1.5 Volt AA battery"

Could some electronics guru please shed some light 
on this ? Several Web sites(please check list below)
have schematics and flashy color photographs of 
single white led light powered off a single 1.5 Volt 
AA battery.
http://cappels.org/dproj/ledpage/leddrv.htm
http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/
dinspirations.com/appliedcontent/Projects/Proj-WhiteLEDDrvr/Proj-WhiteLEDDrvr.html
As most of these are very simple, I have simulated 
a number of them with SPICE, but none of them 
produce the advertised results. What is the mystery ?
Some even have supposed oscilloscope traces !! Any 
thoughts hints would be helpful. Thanks in advance.

On Thursday, 13 November 2014 14:18:47 UTC+11, daku...@gmail.com  wrote:
> Could some electronics guru please shed some light=20
> on this ? Several Web sites(please check list below)
> have schematics and flashy color photographs of=20
> single white led light powered off a single 1.5 Volt=20
> AA battery.
> http://cappels.org/dproj/ledpage/leddrv.htm
> http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/

<snipped - didn't work, with error 404>

> As most of these are very simple, I have simulated=20
> a number of them with SPICE, but none of them=20
> produce the advertised results. What is the mystery ?
> Some even have supposed oscilloscope traces !! Any=20
> thoughts hints would be helpful. Thanks in advance.

The "mystery" is that a white-light LED is actually a blue-emitting LED exc=
iting a broad-band - white light - phosphor, and blue-emitting LED's need m=
ore than 1.5V of drive.

http://en.wikipedia.org/wiki/Light-emitting_diode

suggests that blue-emitting LEDs need between 2.48 and 3.7V of forward volt=
age to push any electrons through the junction.

In order to get this kind of voltage out of a 1.5V battery, you need some k=
ind of switched-mode power supply, as described in the first two urls you p=
osted.

Neither description is a particularly detailed. There are a lot of differen=
t ways to use an inductor and some kind of fast switch to turn current draw=
n from a 1.5V dry cell into a rather smaller current at a high enough volta=
ge to drive a blue LED. The better ones can convert more than 90% of the en=
ergy drawn from the battery into current flowing through the LED.

Which one you'd choose in any particular situation depends on what kind of =
inductor you could get your hands on. When I've had access to coil-winding =
machines I've wound my own transformers ....

--=20
Bill Sloman, Sydney

dakupoto@gmail.com wrote in
news:74eddd6b-53e9-4bac-b29d-5cc40e3544a1@googlegroups.com: 

> Could some electronics guru please shed some light 
> on this ? Several Web sites(please check list below)
> have schematics and flashy color photographs of 
> single white led light powered off a single 1.5 Volt 
> AA battery.
> http://cappels.org/dproj/ledpage/leddrv.htm
> http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volt
> s/ 
> dinspirations.com/appliedcontent/Projects/Proj-WhiteLEDDrvr/Proj-WhiteL
> EDDrvr.html As most of these are very simple, I have simulated 
> a number of them with SPICE, but none of them 
> produce the advertised results. What is the mystery ?
> Some even have supposed oscilloscope traces !! Any 
> thoughts hints would be helpful. Thanks in advance.

This class of single transistor blocking oscillator boost converter 
designed to drive a LED from a single cell is colloquially known as a 
"Joule Thief".   Searching for that term with the keywords 'SPICE 
simulation' will find many simulations of varying degrees of accuracy.  
The basic circuit is pretty forgiving, and can easily be got working with 
junk-box parts which accounts for its popularity.

If the simulation doesn't model non-ideal behaviour of key components to 
a reasonable level of accuracy, it will *NOT* produce realistic results.
Have you accounted for the cell's internal resistance, the resistance of 
the transformer primary, transformer core saturation, the LED's junction 
capacitance and the transistor's gain falling at high collector currents?

Post your simulations (preferably in LTSPICE format) and the observed 
results you are trying to match up with and chances are, someone will 
point out what you've missed.

-- 
Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED) 
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk 
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

In article <74eddd6b-53e9-4bac-b29d-5cc40e3544a1@googlegroups.com>,
 <dakupoto@gmail.com> wrote:
>Could some electronics guru please shed some light 
>on this ? Several Web sites(please check list below)
>have schematics and flashy color photographs of 
>single white led light powered off a single 1.5 Volt 
>AA battery.

You can see an explanation of this sort of circuit at

http://en.wikipedia.org/wiki/Joule_thief

I suspect that your SPICE simulations may not have worked, because you
may have modeled the inductor as a normal "theoretically perfect" one
(which is linear).  The joule thief circuit depends pretty heavily on
the fact that it uses an inductor with significant amounts of
nonlinearity in its behavior - the ferrite core of the inductor
saturates at sufficiently high current levels.

dakupoto@gmail.com wrote:
> Could some electronics guru please shed some light
> on this ? Several Web sites(please check list below)
> have schematics and flashy color photographs of
> single white led light powered off a single 1.5 Volt
> AA battery.
> http://cappels.org/dproj/ledpage/leddrv.htm
> http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/
> dinspirations.com/appliedcontent/Projects/Proj-WhiteLEDDrvr/Proj-WhiteLEDDrvr.html
> As most of these are very simple, I have simulated
> a number of them with SPICE, but none of them
> produce the advertised results. What is the mystery ?
> Some even have supposed oscilloscope traces !! Any
> thoughts hints would be helpful. Thanks in advance.
   Dear electronic idiot: learn to read and understand a schematic!
   If you claim that your SPICE "simulation" did not work,then that 
indicates your ignorance in electronics.

Bill Sloman wrote:
> On Thursday, 13 November 2014 14:18:47 UTC+11, daku...@gmail.com  wrote:
>> Could some electronics guru please shed some light
>> on this ? Several Web sites(please check list below)
>> have schematics and flashy color photographs of
>> single white led light powered off a single 1.5 Volt
>> AA battery.
>> http://cappels.org/dproj/ledpage/leddrv.htm
>> http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/
>
> <snipped - didn't work, with error 404>
* Both references worked for me.
   Both show a complete schematic that works.
   You seem to be communicating with an electronic idiot.

>
>> As most of these are very simple, I have simulated
>> a number of them with SPICE, but none of them
>> produce the advertised results. What is the mystery ?
>> Some even have supposed oscilloscope traces !! Any
>> thoughts hints would be helpful. Thanks in advance.
>
> The "mystery" is that a white-light LED is actually a blue-emitting LED exciting a broad-band - white light - phosphor, and blue-emitting LED's need more than 1.5V of drive.
>
> http://en.wikipedia.org/wiki/Light-emitting_diode
>
> suggests that blue-emitting LEDs need between 2.48 and 3.7V of forward voltage to push any electrons through the junction.
>
> In order to get this kind of voltage out of a 1.5V battery, you need some kind of switched-mode power supply, as described in the first two urls you posted.
>
> Neither description is a particularly detailed. There are a lot of different ways to use an inductor and some kind of fast switch to turn current drawn from a 1.5V dry cell into a rather smaller current at a high enough voltage to drive a blue LED. The better ones can convert more than 90% of the energy drawn from the battery into current flowing through the LED.
>
> Which one you'd choose in any particular situation depends on what kind of inductor you could get your hands on. When I've had access to coil-winding machines I've wound my own transformers ....
>

On Friday, 14 November 2014 09:48:48 UTC+11, Robert Baer  wrote:
> Bill Sloman wrote:
> > On Thursday, 13 November 2014 14:18:47 UTC+11, daku...@gmail.com  wrote:
> >> Could some electronics guru please shed some light
> >> on this ? Several Web sites(please check list below)
> >> have schematics and flashy color photographs of
> >> single white led light powered off a single 1.5 Volt
> >> AA battery.
> >> http://cappels.org/dproj/ledpage/leddrv.htm
> >> http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/
> >
> > <snipped - didn't work, with error 404>
> * Both references worked for me.

There were three url's in the original post - I'd snipped the one that didn't work, and marked the snip.

<snipped the rest>

-- 
Bill Sloman, Sydney

On Thursday, November 13, 2014 7:02:01 AM UTC-5, Ian Malcolm wrote:
> dakupoto@gmail.com wrote in
> news:74eddd6b-53e9-4bac-b29d-5cc40e3544a1@googlegroups.com: 
> 
> > Could some electronics guru please shed some light 
> > on this ? Several Web sites(please check list below)
> > have schematics and flashy color photographs of 
> > single white led light powered off a single 1.5 Volt 
> > AA battery.
> > http://cappels.org/dproj/ledpage/leddrv.htm
> > http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volt
> > s/ 
> > dinspirations.com/appliedcontent/Projects/Proj-WhiteLEDDrvr/Proj-WhiteL
> > EDDrvr.html As most of these are very simple, I have simulated 
> > a number of them with SPICE, but none of them 
> > produce the advertised results. What is the mystery ?
> > Some even have supposed oscilloscope traces !! Any 
> > thoughts hints would be helpful. Thanks in advance.
> 
> This class of single transistor blocking oscillator boost converter 
> designed to drive a LED from a single cell is colloquially known as a 
> "Joule Thief".   Searching for that term with the keywords 'SPICE 
> simulation' will find many simulations of varying degrees of accuracy.  
> The basic circuit is pretty forgiving, and can easily be got working with 
> junk-box parts which accounts for its popularity.
> 
> If the simulation doesn't model non-ideal behaviour of key components to 
> a reasonable level of accuracy, it will *NOT* produce realistic results.
> Have you accounted for the cell's internal resistance, the resistance of 
> the transformer primary, transformer core saturation, the LED's junction 
> capacitance and the transistor's gain falling at high collector currents?
> 
> Post your simulations (preferably in LTSPICE format) and the observed 
> results you are trying to match up with and chances are, someone will 
> point out what you've missed.
> 
> -- 
> Ian Malcolm.   London, ENGLAND.  (NEWSGROUP REPLY PREFERRED) 
> ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk 
> [at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

Yes, I agree totally that unless the non-linearities in the key inductor 
behavior are modeled correctly, the 
SPICE simulation would work. As for 
the transistor, I have used the standard
SPICE model for 2N4401. The diode 
has not yet been inserted. I was just
trying to see if the oscillations could 
be simulated first. Unfortunately, I 
use HSpice at work, and Ngspice at 
home(the simulations were done in my
spare time), both of which use text
based source files as input, as opposed
to LTSpice's GUI based format.
   

On Thursday, November 13, 2014 5:45:56 PM UTC-5, Robert Baer wrote:
> dakupoto@gmail.com wrote:
> > Could some electronics guru please shed some light
> > on this ? Several Web sites(please check list below)
> > have schematics and flashy color photographs of
> > single white led light powered off a single 1.5 Volt
> > AA battery.
> > http://cappels.org/dproj/ledpage/leddrv.htm
> > http://www.electroschematics.com/6195/high-efficiency-led-with-1-5-volts/
> > dinspirations.com/appliedcontent/Projects/Proj-WhiteLEDDrvr/Proj-WhiteLEDDrvr.html
> > As most of these are very simple, I have simulated
> > a number of them with SPICE, but none of them
> > produce the advertised results. What is the mystery ?
> > Some even have supposed oscilloscope traces !! Any
> > thoughts hints would be helpful. Thanks in advance.
>    Dear electronic idiot: learn to read and understand a schematic!
>    If you claim that your SPICE "simulation" did not work,then that 
> indicates your ignorance in electronics.

Dear electronic genius, pray pass on some
of your deep and profound knowledge in the subject, so that guys like me can read and understand schematics correctly.

On 2014-11-14, dakupoto@gmail.com <dakupoto@gmail.com> wrote:

> home(the simulations were done in my
> spare time), both of which use text
> based source files as input, as opposed
> to LTSpice's GUI based format.

unfortunately (for you) LTSpice has become the lingua franca 
for sharing simulations in this newsgroup, mainly because the
price is right *1, it'll run on anything *2 and it's easier 
to use than ms-paint *3

The save format is an ASCII *4 netlist with some embedded GUI 
layout information, it can run other ASCII netlists.

*1 Free download

*2 Well, anyting with an x86 cpu - it runs OK in wine, and
whatever it is that recent macs use to run windows apps

*3 if your goal is drawing electronic schematics

*4 If you tell it to use 'u' for micro, there's a checkbox 
somewhere,else Windows-1252.

-- 
umop apisdn