When batteries don't give enough juice to gadgets, you think that they are completely dead. But, all of them still have plenty of volts, and with a simple circuit you can unlock all of that power. This instructable makes an LED lamp which will suck all of the juice out of those batteries. If i had rechargeable batteries, such as sanyo's eneloop, I would never need to do this.

This is whats called a "joule thief" and it is an adaptation of those.

Step 1: Parts

You will need:
1 3904 transistor
Some 3 volt Super-bright LED's
1 1000 ohm Resistor
1 Ferrite Torroid
2 Different Colors Of Wire
1 AA Battery Holder
Shrink Wrap Tubing
8 in. of Heavy gauge wire
Altoids Tin
Cheap Wire
Soldering Iron & Solder
Wire Strippers and Cutters
I wish I could something like this.
Can this be used for commercial purposes?<br /> <div id="refHTML">&nbsp;</div>
What if i use NOT dead batteries? And please explain me how it works Thanks
It would give too much volts for your LED and the LED might go broken.<br />
can someone please tell me the dimensions of the toroid as im trying to get one fom maplins?<br />
Well pretty much any size will work. About one-two centimeters is good. From a old computer motherboard you will get couple that works fine.<br />
can u give me an idea of the specs for the toroid when its <strong>made</strong> (meaning after the wiring...) i wanna build a smaller version of this so im just gonna get an already built one of these<br/>
10 windings of each wire
sounds about right joule thief uses 8 thanks
Add the length of the wires IS "Take 2 same lengths of wire " Recommend "Take 2, 10(??} inch lengths of wire" Bob
That depends on the size of your toroid, just take enough to get 10 winds...
This is a good instructable. I see you saw the 'Joule Thief' HOW TO in MAKE Magazine. One thing to note is that you should include a schematic. All these written steps are good, but they can get a little confusing. I had to link to <a rel="nofollow" href="http://www.evilmadscientist.com/article.php/joulethief">THIS</a> site to build mine properly. <br/>
will i get the ferrite toroid in a white bulb?
What size is the toroid?
Where does the resistor go. thanks great ible
one end to the middle transistor and the other to the non twisted toroid wire.
Cool thanks i figured it out
whats the purpose of the toroid in the circuit???pls help
can i use speaker magnet as a toroid?
i don't think.
Nice Project. Just a question though; would there be any difference if you used a small one, and did, say only a few wraps, then if you used a huge one and wound it very, very tight? Anyway, again, nice project. I used the design to light a green LED in my "mini" light saber. It's made out of a car cigarette adapter and a mini hot glue stick. I had only room for one AAA.
Oh, in case you didn't figure it out, the first question is about the Ferrite Torroid. I forgot to mention that.
There prob. wouldn't be any difference, as long as its the same basic idea.
what if I wanted a slow flash, like a lighthouse (I know a lighthouse does not flash but has that effect because of rotating source)
you can buy flashing leds or you could make a simple flasher circuit with a couple of transistors.
You might use the cylon eye circuit for a light house. It could use more power than is available here. Just divide the lights up around the cardinal points and away you go.
i don't know, you'd probably need a 555 timer circuit
how long can the thing stay on for?
on a dead battery with half a charge, probably 2 days before it gets very dim.
but he is.....
great ible! is the Heavy gauge wire required? also, where can you get a Ferrite Torroid? thanks.
the heavy gauge wire is not required, its only for the neck. You can find toroids at radioshack, or on their website if you type in "toroid"
can't you make a super charged Ferrite Torrid if you drilled a hole on a rare earth magnet ???
nope, doesn't work that way. I'm not certain, but I think you would just end up with a very biased core that would saturate constantly in one direction.
OK a challenge for the people in Instructables. How can I make a super charged Ferrite Torrid ??
Define "super charged Ferrite Torrid" and what you expect out of one.
OK ill give an example: make a electromagnet 5 times more powerful
that's what i mean by super charged
Nah, you might be able to increase the field strength of the magnet slightly, depending how strong it was to begin with. But no, It's not magic.
so if I get a more powerful magnet to make a one I can get higher voltage from the torrid
No. All using a magnet does is starts you with I biased core. Not really helpful. I guess a better question would be "What are you trying to do?" The voltage output from this type of circuit is pretty decent already. There's ways to get more, but they're generally going to involve more electronics, not just changing your core material.
OK a noob question what is biased ( define in the electrical terms plz.)
It just means that the core is already magnetized in one direction. I don't think it'll help in any way. It may allow slightly more energy storage than you would get otherwise, however, since a magnet probably isn't the best core material to start with. I don't want to sound negative or anything. But you really should try and learn the basics first, before you worry about creating some revolutionary new super-toroid. If it were that easy, it would have been done already. Start by learning DC stuff, voltage/current/resistance. Ohms law, etc. Then learn some AC stuff, Inductance, Capacitance, etc. Once you understand all that, then you can start looking at the details of how an inductor works magnetically. It's not the simplest concept out there, and without a grounding in the basics, you're not going to get anywhere with it.
I would think a magnetized core would choke the windings, decreasing the power output. As a rule transformers use an iron core alloy that doesn't magnetize and, stay magnetized.
I'm just thinking out loud here since I'm no expert on magnetism, but if you used a "permanent" magnet, it should return to its original state in the end (no extra hysteresis losses?). I think it might saturate much more easily in one direction though. That said, it's not going to give the coil any superpowers. In general it's going to make things worse.
i have studied the stuff you mention above but i just had no idea how a torrid works. that's the reason why i was asking.
Okay, well, A toroid is just like any other inductor. They use them because the field is pretty much fully contained so they cause less EMI.
Thanks for your help
couldn't you just wire in 2 diodes going into 2 different bits of wire wound in different directions? i mean have the diodes arranged so AC can pass. would that work?

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