Step 4: Try it Out!

And that's it! You're finished with your Joule Thief. Touch the twisted wires coming from your toroid to the positive side of a battery, and the extension wire to the negative side. If all is working well, the LED will light up! If not, try using thinner wire on your toroid. I've included a schematic in the pictures if you prefer.
<p>Hi, I tried making the same circuit but i don`t know what is wrong it`s not working i used the npn 2n2222 instead of a npn 2n3904 and i followed the same steps shown here but i can`t figure out why my circuit isn`t working? plz help i need it urgently!</p>
<p>You need a wire from the LED's negative to the battery.</p>
<p>I used a 2N3904 or 2N2222 going into a tip 31. It ran a solar led garden light that had a joule thief in it ran by my second joule thief. I got rid of the battery and replaced it with a 100F capacitor charged to 1v. It draws 2.6 miliamps. </p>
<p>My transformor was a bifillar toroid over rubberized ferite. And the choke was from a pc tower power supply. With a few of 10 pf capacitors. I just posted the circuit as the board migh be too confusing with that darlington array on it or what was a modifed darlinton pair. And that may not be perfectly drawn. PNP transistors would have worked better I think also. </p>
<p>You can use the digikey site to draw circuits as well. </p>
Mine is coming on but it is not getting brighter and the voltage is the same. I use a 13003 transistor. Please some help.
<p>Would it be better to use a N channel MOSFET in place of the NPN bipolar transistor? There's usually a 5V reverse bias limit on the base-emitter junction, a FET could allow more negative voltages on its gate (e.g with a. lower turns ratio), plus it's more efficient because there's no saturation voltage drop. I guess you'd also have to watch that the steady state (DC) condition of the transistor being on permanently which could short the battery, but a nice little circuit!</p>
<p>Hey thank you for your help with building my little dog light, now an Instructable!</p><p> <a href="http://www.instructables.com/id/Joule-Thief-Dog-Light">http://www.instructables.com/id/Joule-Thief-Dog-Li...</a></p><p>I couldn't have done it without your own great Instructable.</p>
<p>i have been trying with many transistor/wire/battery nothink working :c </p><p>What's wrong ?</p>
<p>emitter/collecter seems both to be connected to -</p>
<p>emitter/collecter seems both to be connected to -</p>
<p>What resistor are you using?</p>
<p>You could check all components, if there is current through them.Try &quot; ordinary&quot; wire ,instead of cobber wire for the toroid, unless you have current flowing through ofc ( they can be a bit difficult to get stripped right ),Check led works ( i dunno why you shrinktubed it ) it is easier not to, when starting up, get polarity right. :) That is all i can be helpfull with. Hope it works out fine.</p>
<p>Resistor is 1.2k the only one i was having on hand , i just tryed with some other wire same result , led is ok , i also tryed with a 920 ohm same result .</p><p>I have no luck with that sort of circuit i think :,), </p>
<p>Your circuit dosent quite seem right, from what i can see.This is what i can show.Remember transistor NPN.</p>
<p>Ok here they are,all 3 J-Thieves.Was fun to make them.I want to make more, smaller,wierder.</p><p>Can any tell how bedst to measure lightintensity without a lightmeter? To measure effency in circuit?</p><p>If it is possible</p>
<p>Wanted to make a smaller but as i am learning it will come.</p><p>Actually fun to make your own pcb.</p>
<p>Another J-thief.Random,casual,carefully handpicked vintage components. :)</p><p>Solderwork looks crappy and is.I`m a novice.</p><p>J-thief rox.</p>
<p>hello , could a s9014 work ?</p><p>thanks</p>
<p>:) my 1.st.Tis loads fun.Just the beginning.</p><p>Ty for tutorials.</p>
<p>Ps it is a 1 watt button led.</p>
I used BC549C to build a Joule Thief.
Does not work with 1.5V and 421 2DT nor with BC 337-40, only at 3-5V.
<p>In my experience dead CFL's are not a reliable source for toroid's as they are often too small to be useful in a project like this.</p>
Would a 2N3906B work i don't know about transiters
<p>You can, but you have to reverse the polarity of the supply and the LED on the circuit.</p>
<p>Here's a schematic for a PNP version: <a href="http://2.bp.blogspot.com/-nKDPBXQ1fhg/VLyHUdlfIZI/AAAAAAAABsY/7D6-sx2EI1s/s1600/pnp-joule-thief-wiring.png" rel="nofollow">http://2.bp.blogspot.com/-nKDPBXQ1fhg/VLyHUdlfIZI/...</a></p>
<p>Here's a schematic for a PNP version: <a href="http://2.bp.blogspot.com/-nKDPBXQ1fhg/VLyHUdlfIZI/AAAAAAAABsY/7D6-sx2EI1s/s1600/pnp-joule-thief-wiring.png" rel="nofollow">http://2.bp.blogspot.com/-nKDPBXQ1fhg/VLyHUdlfIZI/...</a></p>
The 2N3906 is a PNP transistor. The circuit requires a NPN transistor like the 2N3904 or the 2N2222.
Hey :) I am making a mini wind turbine and my motor generates about a 1V . With the joule thief I get 1.5V . How to get ~4.5V ? How to do it? Is it possible?
Increase the number of turns on your toroid and use a higher rated transistor. With 200 turns of the primary coil and 8 of the secondary, you can get approximately 110v, enough to power a CFL from an AA battery...but only for about 20 minutes. A D battery has a larger energy density and capacity, and may last upto an hour powering a CFL. The circuit doesn't actually do any boosting. It merely oscillates the voltage at a high frequency, which tricks electronics into powering up. A rapid recording would show that the light actually turns on and off at such a high rate, to our eyes appears to be lit solid.
<p>would adding a small capacitor help then? Or would it drain it too fast, maybe if the capacitor was minimal, you wouldn't want the cap to be Over charging, just right on the threshold.</p>
And by secondary and primary what do you mean........ Could you tell which one goes for the base and which one for the collector?
Did it work?we have common problem.im also making wind turbine and my motor generate also about 1V.<br>charingweedworm69@gmail.com
<p>Here is the schematic. This is all over the net. I would like to make this with 2 batteries for even longer life, but I suspect this will significantly increase the LED current. Any ideas?</p>
<p>Connect your 2 batteries in parallel. Voltage will be the same. Assuming you have 2 1.5V batteries, connecting in parallel will give you 1.5V but with a higher amps. </p>
<p>The pictures are great, thanks. But, this really needs a real schematic. I can't quite tell how you're connecting the coil. </p>
<p>I used 2N2222 transistor. The circuit was not working. why?</p>
<p>Why don't you just recommend using the 2N4401 transistor instead of the 2N3904? Is the 2N3904 more common to see in stores?</p>
Would a CTBC 547B LE work, i got it with DIY kit still in new condition <br>
I used transistors of dead cfl lamps which is 13002,13003.. but the joule thief isn't working.. can i use any other transistors thats NPN or is it specific to use 2N3904, 2N4401?
<p>I have used 13003 transistor on a joule thief circuit, so I know it works, dead CFL's are not very reliable source for transistors as sometimes when the bulbs goes bad, transistors burn out too. (Often it's the transistors that fail in these bulbs). Also take note that pinout on these transistors are not standardized between manufactures, I have TO-92 13001 that has pinout reversed (BCE).</p>
<p>I need your suggestion and help, from a source I am getting 100 mV and 50 microAmp (&micro;A) not milliAmp (mA) current continuous mode. Can I use jewel thief circuit to light a LED. if yes please let me know the resistor in ohm, diode specification and led specification so that i can make the circuit and how many wire turns will be required. To enhance the density, can I use capacitor for this small production of what specification. Please help</p>
<p>You need bigger power supply, the Joule Thief circuit only increases voltage, not current, if the current is too low the circuit simply doesn't operate. Also it's not that efficient as it also draws current.</p>
<p>Jewel thief :D</p>
<p>haha ... i noticed it a little later.. </p>
<p>You must know that a white led's voltage need to be around 3 V, and it draws about 20 ma to be lit up. Can you tell me what power source you have, and what project you re working on, so we can help</p>
Could I substitute the 2N3904 transistor for a TIP3055?
<p>It's a NPN 15A 60V transistor and it should work fine. </p>
<p>As long as it is a NPN, you can use it. Check the pinout schematic. The higher rate the transistor can handle the better</p>

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