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Blinking joule thief

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anfegori91

New Member
Why my joule thief is turning on and off the led ? (I know, that is what actually does).. but it was on for 2 days approx, and now is flashing ~30 seconds off, ~10 seconds on; first it was flashing ~30 seconds off, 20 seconds on.

-update: ~5 sec on, ~50 sec off.
 

Sceadwian

Banned
This is normal for a joule thief, I've had the same experience. What happens is the battery draw is constant and drops until the dropout voltage of the diode is reached in which case the battery current drops to near zero, thing is, battery voltage will gradually refresh to some degree over time under no load until oscillation can once again occur and the LED comes back on, again until the voltage drops too low and it turns off. I had a joule thief on a single battery blinking for over a week. The blinking rate will continue to get longer and the on till will continue to get shorter until one day it simply doesn't come back on again.
 
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audioguru

Well-Known Member
Most Helpful Member
Your battery voltage is dying. Replace it with a new name-brand battery.

But since you forgot to post your schematic then we are just guessing.
I know, NOOBs cannot post anything here unless they are approved "Not Spam" by a Moderator. A real nuisance.

When my solar garden lights run out of battery charge then they turn on for 1 second then turn off for 10 seconds over and over for hours. Their voltage step-up circuit is similar to a Joule Thief.
 

RODALCO

Well-Known Member
That is perfectly normal for a Joule thief.
The (exhausted) battery voltage is probably around 0.4 Volts when it switches off.
 

anfegori91

New Member
the schematic:

8926-1828270262_b76c867954.jpg


the whole article can be found here:
Weekend Projects with Bre Pettis: Make a Joule Thief - Evil Mad Scientist Laboratories
 

RODALCO

Well-Known Member
That is the Joule Thief, I have used the same circuit and it works well.
 

Nick_de

New Member
Hello Everyone,

I'm new to this forvm as much to electronics... I have built my first joule thief and it kinda works: I get light only when rubbing one of the leads against the battery! If I leave the leads to the battery correctly in place I see nothing...
The schematics used is already above... Does anyone have an explanation or I might try?
Does the LED have to be white or blue? Or can it also work fine with red, yellow, etc?
Thx in advance

Nick
 
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Nick_de

New Member
I solved it: I change resistor to a lower value... But why doesn't 1k work for me?
Can it have something to do with the "quality" of my coil around the toroid? The battery is fine...
 
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audioguru

Well-Known Member
Most Helpful Member
Maybe you connected the collector and emitter pins of the transistor backwards.
 

RODALCO

Well-Known Member
The Joule thief works with any colour LED.
You can even put two or three led's in series.
 
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