Joule Thief

[Pirate88179]

Xee2:

That is a good question.  My guess is that if he stops it, it may have to be "jump started" since he is already below what the transistor is supposed to require.

If it does not start again, maybe he could take another AA and hook it into the circuit and then, once running, remove it?

Bill

[dllabarre]

Xee2:

That is a good question.  My guess is that if he stops it, it may have to be "jump started" since he is already below what the transistor is supposed to require.

If it does not start again, maybe he could take another AA and hook it into the circuit and then, once running, remove it?

Bill

I disconnected the battery for 10 seconds.
Reconnected the battery and the LEDs did not restart.
I watched the battery as it "bounced" back to 351mV then the LEDs lit up real bright.  Then of course the battery started dropping back to where it was ~284mV and the LEDs are dimmer again but still lit.

DonL

[kooler]

ok
i finally got some pics

http://img195.imageshack.us/i/1020716.jpg/

http://img15.imageshack.us/i/1020717.jpg/

the secondary windings are speaker wire also... three turns almost..
and the jt circuit has a 1k resistor and a small cap across the batt
with a little over 2 volts showing
what i am trying to figure out is why the leds are lit but have a forward voltage of 3.4 at 100ma's

thanks,
robbie

[jeanna]

ok
i finally got some pics

the secondary windings are speaker wire also... three turns almost..

what i am trying to figure out is why the leds are lit but have a forward voltage of 3.4 at 100ma's

Good job robbie,

I think there are a few reasons the lights are lit.

First-  you are not able to see how high the voltage spikes really are on your DMM.
So, you probably have spikes that are at least 12 volts high.
Perhaps more, although with only 3 turns maybe just 12v.
You might have a pretty high frequency of spikes too.
That frequency is determined by the resistor at the base of the transistor plus some other things.

Second-  these super bright are partly regular leds and partly they are something else like teeny fluorescent bulbs.

The lights are actually blue and they paint the fluorescent paint on them which is  yellow to add to the blue to show white.
But now since this is fluorescent paint, it can behave that way IF you give it high enough voltage.
You don't need eeven the milliamps of the usual led.

I have seen mine work in 2 directions. Not often but in some circuits.

So, there is my take on it, for what that is worth.

jeanna

[stprue]

Good job robbie,

I think there are a few reasons the lights are lit.

First-  you are not able to see how high the voltage spikes really are on your DMM.
So, you probably have spikes that are at least 12 volts high.
Perhaps more, although with only 3 turns maybe just 12v.
You might have a pretty high frequency of spikes too.
That frequency is determined by the resistor at the base of the transistor plus some other things.

Second-  these super bright are partly regular leds and partly they are something else like teeny fluorescent bulbs.

The lights are actually blue and they paint the fluorescent paint on them which is  yellow to add to the blue to show white.
But now since this is fluorescent paint, it can behave that way IF you give it high enough voltage.
You don't need eeven the milliamps of the usual led.

I have seen mine work in 2 directions. Not often but in some circuits.

So, there is my take on it, for what that is worth.

jeanna

You are right Jeanna, this is why the leds light for him!