Joule thief?

Is there a joule thief capable of powering a 3 watt LED at full brightness? Or just over 300ma output average?

Asked by .Unknown. 8 years ago  |  last reply 8 years ago

Joule thief is not working. Answered

I just made a joule thief and my led is not lighting up. I put a single AA and it wont power. My led does though require 3.6v and i gave it 3.7v for a few seconds and the transistor became extremely hot. Is there something i am doing wrong? I have a 1k resistor, a 2N2222 transistor, a led that requires 3.6v and 30ma, regular wire 26 awg, and a toroid bead.

Asked by Munchys 8 years ago  |  last reply 7 years ago

Joule Thief Troubles

I have built several Joule Thieves as seen in this video. None of them worked. Is the schematic wrong? I am sure that I used all the right components, and I wound the transformers right... What could be the problem? Could it be the ferrite core? I used one from an old computer power supply. Any help would be appreciated.

Posted by 1up 11 years ago  |  last reply 7 years ago

Joule thief is not working?

Learned about the Joule Thief from Make's Magazine and used their schematic. I'm pretty new to electronics so I don't know much about components. Applying 3 V, the LED lights up, but applying 1.5 V, no light. Green wire is 22 ga, blue wire is 26 ga. Using a 2N3904 Transistor and a Ferrite Toroid. I think I "barely" got the LED to dimly light up, but it would not stay on. Am I doing something wrong? Picture available in second comment.

Asked by gera229 4 years ago  |  last reply 4 years ago

Joul thief how to? Answered

I've been reading some ibles about joul thief making, and most of them teach how to power an LED with a 1.5v AA battery.  That is great, if you want to power an LED with a 1.5v AA battery :) But what if I want to keep using old, weak AA batteries, as 1.5v batteries?  How do I make a joul thief that takes whatever the battery can give it, and outputs it as 1.5v?  I know the kind of transistor, ferrite core, number of windings and wire gauge all affect output, so how do I know what to use? Thanks!

Asked by Morgantao 5 years ago  |  last reply 5 years ago

IWhat will happen if I hook 2 joule thieves together?

I want to hook 2 or more joule thieves together so that the voltage will increase much more. Will this work to have one generating 3 volts and have that hooked up to a second, generating 6? Also, how many milliamps does one joule thief generate, and would that number double too? Also, what sort of resistors would I need for the increasing voltage with each one? I have an instructable idea that would involve them being hooked up to a motor to generate electricity, and if you can help me we can collaborate on it.

Asked by XOIIO 8 years ago  |  last reply 8 years ago

can any NPN transistor be used to make joule thief.....and 1kohm resistor is only necessry to make it???????????

Iam making joule thief....................can i use any Npn transistor to make it and only 1kohm resistor be use??? it work on different value of resistor.............?????????

Asked by rachit59 9 years ago  |  last reply 8 years ago

My joule thief Lights my LED for a second then dies, can anyone help? Answered

My joule thief Lights my LED for a second then dies, I could only make it flicker by scratching two of the connections. I've used three different transistors but received the same result. The transistors were kn2222, pn2222 and 8050 (couldn't find Bc547,2n2222 etc). I had 18 loops around the toroid and a 100 ohm resistor, is there anything wrong with this and can I fix it?

Asked by Zithe 7 years ago  |  last reply 7 years ago

joule thief: can i use a cellphone battery charger to power a joule thief? output 5v~ 400-600mah. Answered

What resistor should i use? a 1k resistor,220ohm or a variable resistor/potentiometer B50K is ok?  masters help pls.. im noob

Asked by reopoop 5 years ago  |  last reply 5 years ago

Would a joule thief work on a lager scale like 20 plus 1.5 volt batteries at a time?

At my dads work they throw away barely used D and C batteries I would like to use them to power and charge devices.

Asked by adamz 9 years ago  |  last reply 9 years ago

How many windings do I need on a toroid to make a joule thief work?

How many windings do I need on a toroid to make a joule thief work? Is there a min and or max number of winding? Is the toroid acting as a one-to-one transformer? Can I use anything as the iron core? Is there a calculation to find this out? Thanks for any help.

Asked by daemonral 9 years ago  |  last reply 9 years ago

im trying to build a joule theif but im not very experienced can somone help? i need dimensions aswell?

The only place i can get the components is maplins can somebody link to the right product or give me the dimensions? thx

Asked by wizzywoo 9 years ago  |  last reply 9 years ago

How would i used a joule theif and power 10 to 50 led on a circuit if i used a 5v power supply or a battery.?

I wuld like to make a banner out of leds for my wife and i am wondering if it would b possible to do it using the joule theif method but instead of a battery use a 5v power supply. wat resistor wuld i need and is it even possible?

Asked by tak332 6 years ago  |  last reply 6 years ago

Can this be a coincidence? Do they look like two independent designs? Answered

I came across this kit when I was browsing the web. What surprised me is the uncanny resemblance to my design published here in Instructables. I'd like to know what you guys think about those two designs. Do they look like they are created by two independent designers? Can someone design a product so similar to another without copying the other? (The kit in the front part of the picture is taken from Eastern Voltage Research website. The photo is photoshopped by them since yesterday to remove holes on the end of the PCB which accomodate home made battery clips.) Please post your opinions! Thank you!

Asked by ledartist 6 years ago  |  last reply 6 years ago

how does a toroid in Joule Thief circuit work? Answered

Sorry for the noob question, but i can't understand how a toroid can cause a LED with higher voltage than the source to be lit.. i tried to make it without the toroid (only the transistor) but it didn't work... any explanation is much appreciated.. tq..

Asked by firdaus_alizh 9 years ago  |  last reply 7 years ago

Joule thief's....? Answered

Do all the components make a difference in the efficiency of the joule thief? i.e type of transistor, resistor, capacitor...

Asked by ML159 9 years ago  |  last reply 9 years ago

solar joule thief and iPod?

I want to charge my iPod using a joule thief circuit and a solar panel. I don't know the voltage or current output of the panel and I also don't want to fry my iPod.

Asked by evilmadscientistman 9 years ago  |  last reply 9 years ago

joule thief without resistor?? Answered

I want to make a joule thief,  but I don't have the 1k ohm resistor, so what can I use instead? or will it work without the resistor? Thanks for answer!

Asked by aninda13 4 years ago  |  last reply 4 years ago

How to build a joule thief? Answered

      I'm building a voltaic cell and a joule thief. I searched on some instructables and followed the one on youtube by MAKE:. When I hook up a 9V for a few seconds (To not burn the LED out), it works. However, a AA doesn't work. Not even a brand new one. So, I presume that I haven't wrapped the toroid around enough to create more voltage and lessen the amperage (If that's what joule thieves do)? I posted some pictures below. Also, I'm looking to buy a voltmeter, I'm around basic level and just need to measure if the joule thief is even increasing voltage (For now at least). Here are some cheap ones I'm looking at on amazon: Some of those have autoranging, is this to automatically find the voltage/amperage? Thanks, please reply

Asked by knexpert1700 5 years ago  |  last reply 4 years ago

Joule Thief Speaker Amp?

If a joule thief circuit can be used to amplify a battery to power an LED, could it possibly be used to amplify a speaker instead of a LM306? chip?

Asked by tinstructable 8 years ago  |  last reply 8 years ago

Coilgun, Mosfet problem and joules?

I have two questions: when a mosfet is damaged, it conducts electricity without putting energy to the gate? I have the 75N75 mosfet and I want to use it on the rwilsford07 boost converter, but the mosfet didn't work and I don't know why it conducts energy without putting energy to the gate. I read that the mosfet can be damaged with static electricity, but I use always an anti-static wrap. The formula to get the joules from a coilgun is this?: 0.000005 * C * V * V C= uf V= voltage

Asked by Kurt Gerhard 7 years ago  |  last reply 7 years ago

Joule thief 12VDC 3A?

Is it possible to build a joule thief to run a netbook? I mean feeding the circuit with a 9V radio battery and to have an output of 12VDC 3A.

Asked by laurieddhru 6 years ago  |  last reply 6 years ago

A More efficient joule thief Answered

I need to make a joule thief type of thing that can up the power from a 0.55V source to a simple LED. I know that the joule thief is not the most efficient circuit which is why I am asking if you know of an efficient circuit I can use.

Asked by physics_dude 8 years ago  |  last reply 4 years ago

Joule thief running a CFL?

I've seen a lot of videos of people making joule thieves to power CFLs, with only one or two cells. (These actually work, right?) However, most of them require large (larger than a soda can) inductors and/or ignition coils and transformers. Is there any joule thief (or circuit) out there capable of running a CFL at full brightness, with around 6V, but at the same time being as small and uncomplicated as possible?

Asked by .Unknown. 8 years ago  |  last reply 7 months ago

is there a way to make a joule thief for a 9v battery?

Asked by Slicerr2 7 years ago  |  last reply 7 years ago

Why Isn't My Joule Thief Working ? Answered

Asked by icekid 6 years ago  |  last reply 6 years ago

Can I make a joule thief with Pnp transistor?

I  was making my joule thief recently and I could not get success. I found out that I have Pnp transistors and that's why I am wiring them wrong. Can anyone provide me with a schematic to make it with Pnp transistor?  Thanks for your help!!

Asked by aninda13 4 years ago  |  last reply 4 years ago

I need help on to make a joule thief? Answered

I had made tons of joule thief, but the biggest problem is at beginning I had faced one problem, which is whenever I make it it can light up the led after some shaking,, (shaking causes some wires to touch the other in a way that is correct I guess).  But I follow the schematics, and then I finally made on that worked better, and without any toroid bead, but now with the new transistors I bought, none of them work anymore,  my old transistors got lost. so what can I do? 

Asked by aninda13 4 years ago  |  last reply 4 years ago

joule thief won't work for me, can't figure out the problem

i made joule thief as shown everywhere in instructables, I tried few different transistors, and toroids, I had like 100 tries, and can't get it to work? and: can I use transistors-in the middle of the last picture?

Asked by xtony666 9 years ago  |  last reply 9 years ago

MXDL 3 watt joule thief? Answered

Can anybody make sense of the joule thief inside a MXDL 3 watt luxeon torch? I can post a rough picture of it if needed.

Asked by .Unknown. 8 years ago  |  last reply 8 years ago

3w led with two D cells.

The led is 3,8V drop 800mah, and the bateries are only 2,4-3v, there is any simple circuit to make it work properly? Maybe a joule thief, but i don't know if i can pull 800mah from it. Any sugestions? thanks.?

Asked by notingkool 6 years ago  |  last reply 6 years ago

Which transistor is best for joule thief between BC107 and BC547?

I want to make a joule thief to run led's from my death batteries.I have 2 transistors,BC547 AND BC107. Which transistor should I use to make a low voltage joule thief ?

Asked by Crazynventor 3 years ago  |  last reply 3 years ago

can a joule thief be used for a 6 volt incandescent lantern? Answered

I want to use a joule thief to increase the lifetime of a lantern battery. I want to use the incandescent bulb, it has more power than leds. I plan to have one lantern for new batteries, and one for used batteries with the joule thief.

Asked by cb92 8 years ago  |  last reply 8 years ago

Does a joule thief consume power without a load? Answered

I want to add a joule thief to a battery so it always puts out 12 volts regardless of the charge level but i don't know if it will constantly drain the battery. I am also wondering if anyone has ever used a joule thief with a wind generator to charge batteries.

Asked by AlbinoMoose308 6 years ago  |  last reply 5 years ago

Where can i find a ferrite toroid for my joule thief? Answered

Where can i find a ferrite toroid for my joule thief? Iv'e opened almost all the devices in my house!!! Just wanted to make a simple joule theif. I dont have any CFL's to open.

Asked by TheMasterThingMaker 8 years ago  |  last reply 3 years ago

LEGO Stormtrooper Joule thief mod

Onkelond over at Flickr came up with a great way to make your lego minifigs light up!link

Posted by Zorink 10 years ago

12v joule theif from 1 AA Answered

I need to make a joule theif that can output 12v to power some rgb leds. any help would be great. but preferably in the form of a schematic. i have all of the parts needed.?

Asked by aduy 7 years ago  |  last reply 15 days ago

how to improve a joule thief ? will increase of no of coils help?

Asked by prasanmitnath 6 years ago  |  last reply 6 years ago

Joule thief? Answered

Http:// : It was from here that I built my first working joule thief. (I've found better ones now.) Anyways, last week, I got bored and tried to destroy an LED by feeding the circuit more and more power...I got to 18V (laptop charger adapter) and it still didn't bust. Why?

Asked by .Unknown. 8 years ago  |  last reply 8 years ago

My joule thief is not very bright? Answered

My joule thief is not very bright? I've changed the windings, transistor and the resistor; and it is still pretty dim. Help please Parts: 2 different size toroids: Large and Small 3 Transistors: 2n2222, 2n3904, 2n5830 2 Resistors: 1k, 2.2ohm blue led white led with a heatsink Also I used a 20awg and 36awg to make the toroids

Asked by daemonral 9 years ago  |  last reply 9 years ago

my solar setup wont work with my joule thief, it just bypasses it. why?

I got a few solar cells wired up in a series to produce around 4 volts, so to get more power from it i connect it to a joule thief i made but the power goes through it and isnt boosted at all. the joule thief works. at 1.5volts it makes around 5 volts. so i cut the power on the cells to 1 volt thinking im overloading the circuit but it is still bypassed.  i even connected a couple of capacitors to the solar cell to trick the joule thief into thinking the solar cells are a battery but still no luck. my question is why doesnt the joule thief boost solar cell power but will boost a dead AA battery?

Asked by florlayamp 7 years ago  |  last reply 7 years ago

How do you increase the amps from a joule thief? Answered

          I'm working on a project using the joule thief circuit and when I put multiple LEDs in parallel they all get really dim. Is there anyway I can increase the amps going to the LEDs so they can all shine brightly?                                                                                                                                                                                       I was thinking a more powerful transistor or a larger transformer toroid with more windings. Any suggestions?                                                                                                                                                                                                                                                                                                                                        Here is a link to the circuit diagram:                                                                                                                                                                                                                                                                                                                                                                                  Thanks!

Asked by transistorguy 8 years ago  |  last reply 6 years ago

Is this a Toroid Bead and can it be used for a joule thief? Answered

I found it at the end of a power chord.

Asked by coolpizzadude 8 years ago  |  last reply 7 years ago

Joule Thief w/ 555 timer

Hello, I have a question about using a 555 timer with a joule thief. I'm trying to build a circuit for some solar powered bike lights but I have a couple of questions... 1. Am I correct in assuming that it's a bad idea to try to run a TLC555 timer chip from the output of the joule thief? Without a load, it seemed to be pumping out at almost 80 volts. 2. I tried building the circuit so that the two rechargeable 1.2V batteries would power the 555 directly, and then the output would sink and source two transistors alternately, which in turn would switch the LEDs alternately, using the output from the joule thief, which was also powered directly from the battery. That resulted in no LEDs lit and some very hot transistors... Bad idea. The TLC555 chip is supposed to run on a supply voltage of 2-18V, but when I tested it with the 2.4V coming from the batteries, it would source, but not sink... Is there any way to build this circuit so the 555 could blink 2 LEDs alternately while the LEDs are powered by the joule thief? The only alternative I can see that might work would be to power the joule thief from the output of the 555 and just blink all of the LEDs at the same time from the joule thief's output. Any help would be appreciated!

Posted by amklose 8 years ago  |  last reply 8 years ago

"Joule Thief" LED Night Light Kit is Now Shipping

Thank you so much for those who pre-ordered the kits! I have shipped all orders now, and the kits are in stock. New orders will be shipped within 2 days. To purchase, please go to Please see this post for the pricing and more: Thanks!

Posted by ledartist 7 years ago  |  last reply 3 years ago

Efficient/High output Joule Thief?

Right now, I am looking for schematics for the most efficient (1 cell and 1 LED) joule thief, to use as a durable reading light. I right now favour Quantstuff's 2 transistor SJT ( but I am not sure whether it is the most efficient. I've seen several others, but since they all claim to be equally as efficient, i'll have to rely on the experience of other tinkerers and hobbyists. So: what's the most efficient or high current or high voltage joule thief you know of?                                                                                                                          Thanks.

Asked by .Unknown. 8 years ago  |  last reply 5 years ago

Joule thieves?

I am trying to make a joule thief according to many websites and such, but it never seems to work, even if I follow the instructions. The joule thief I'm trying to make is one of the simplest, with a 1K resistor, transistor, tapped coil, etc. I think it may have something to do with the inductor, even though I've tried a whole different types. I got it to work once, though, when the 1K resistor was replace with a 10K resistor accidentally. I heard somewhere that the resistor should be around 1K up to 3K. Any higher and efficiency goes down. Is that true? And why doesn't the joule thief work when I use a 1K resistor instead of a 10K resistor? P.S: I have made many other joule thieves, my first one being from, and my favourite, the supercharged joulethief from

Asked by .Unknown. 8 years ago

Anyone interested in a stator joule thief? Answered

A few days ago I made a few joule thief ornaments from motor stators and rotors (pictures on my blog). I was wondering if there is any interest in an instructable detailing how to find the right wires on a motor and generally how they can be wired/rewired for joule thievery. Since my recreational project focus is capricious at best (and my blog is very young) I've put the question here rather than there. Alternatively I could write an instructable on the process of making a specific joule theif with a stator, but I would have to not include sections on different types of motor for clarity's sake. So if you have a preference for one or the other, or an interest in the idea, I would appreciate any input. Thanks, Drew

Asked by andy 8 years ago  |  last reply 8 years ago

Does any one know how to make an Ne-2 joule thief ??

Recently I’ve been researching on how high voltage joule thief works. The popular high voltage joule thief videos out there are known as Jeanna’s light if I’m not mistaken. I also built my own little LED joule thief circuit, it appear success after all with a 2n3904. But I want to take the concept a little bit further, so I decided to attempt on the high voltage joule thief circuit. It appear no luck, I have 120 turns for high voltage on my ferrite core (1 turn = 1 volt). I know it’s the same principle as the LED joule thief but with the LED removed. I have two 1kohm resistors and I connected them in parallel to get 500ohm resistance. I connected them all like the LED joule thief, but it seems like I did something wrong.  So I ask for further instruction. Parts that I use: 40 or 30 gauge magnet wire (high voltage windings) 20 gauge magnet wire 2n3904 transistor (Don’t know if that’s the right transistor for this circuit, but it’s for experimental purposes only.) 2x 1Kohm resistors in parallel = 500 Ohm resistance AA rechargeable battery. The thick magnet wire are 7 turns.

Asked by BlackWolf1024 5 years ago  |  last reply 4 years ago