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...

Question by ML159   |  last reply

Joule thief?

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

Question by .Unknown.   |  last reply

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?

Question by .Unknown.   |  last reply

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.

Question by Munchys   |  last reply

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.

Topic by 1up   |  last reply

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.

Question by gera229   |  last reply

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!

Question by Morgantao   |  last reply

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

Question by reopoop   |  last reply

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.............?????????

Question by rachit59   |  last reply

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?

Question by Zithe   |  last reply

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.

Question by adamz   |  last reply

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.

Question by XOIIO   |  last reply

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

Question by wizzywoo   |  last reply

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?

Question by tak332   |  last reply

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!

Question by ledartist   |  last reply

Joule robber - a better joule thief....

I had a look at some of our 'ibles for the famous Joule Thief circuit. While checking a few of the creations and checking their performance I noticed a massive flaw: Only LED's with very low power consumptions can be used. After some trial and error I was able to create a slightly modified version that not only lights white and blue 5mm LED's but also the very powerful Cree Led's - the later would require a suitable transistor to handle the load. I only used a salvaged BC556 transistor, so the LED starts working at around 0.5V, brightness is adjustable within certain limits to cater for the battery state. So instead of using a limited circuit that basically just doubles the input voltage with the focus of extreme low power consumption, my circuit is aimed on single cell battery lamps that might need more power. Using a very low voltage transistor with minimal losses would still provide a power source for batteries that are under 0.5V, while using a bigger transistor like Tip142 or 2N3055 and a modified transformer can drive a CFL lamp from two AA batteries, single cell if you don't mind a warm transistor. Biggest improvement however is that I don't use a toroid core, which makes winding so much easier :) I am not too good in drawing circuits and prefer the direct solder method for my prototypes but if there interest I would take the time to make some pics and draw a circuit for an Instructable. But with so many similar circuits already out there I wanted to get some feedback first.

Topic by Downunder35m   |  last reply

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

Question by .Unknown. 

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..

Question by firdaus_alizh   |  last reply

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!

Question by aninda13   |  last reply

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?

Question by tinstructable   |  last reply

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

Question by knexpert1700   |  last reply

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.

Question by evilmadscientistman   |  last reply

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.

Question by laurieddhru   |  last reply

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.

Question by physics_dude   |  last reply

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?

Question by .Unknown.   |  last reply

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!!

Question by aninda13   |  last reply

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? 

Question by aninda13   |  last reply

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?

Question by xtony666   |  last reply

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.

Question by .Unknown.   |  last reply

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.?

Question by notingkool   |  last reply

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 ?

Question by Crazynventor   |  last reply

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.

Question by AlbinoMoose308   |  last reply

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.

Question by cb92   |  last reply

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.

Question by daemonral   |  last reply

LEGO Stormtrooper Joule thief mod

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

Topic by Zorink 

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?

Question by florlayamp   |  last reply

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

Question by daemonral   |  last reply

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!

Question by transistorguy   |  last reply

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.

Question by TheMasterThingMaker   |  last reply

"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!

Topic by ledartist   |  last reply

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.

Question by coolpizzadude   |  last reply

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!

Topic by amklose   |  last reply

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.?

Question by aduy   |  last reply

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

Question by andy   |  last reply

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.

Question by .Unknown.   |  last reply

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.

Question by BlackWolf1024   |  last reply

How to make Joule Thief with Multiple LED and maintaining its brightness.

I've seen people running 61 LED or 100 LED on Joule Thief (1 AA Batt) with its full brightness. How did they do it?? I know how to build Joule Thief I have: -NPN   2N3904, 2N2222A, 2N4401   Transistors -Resistor   what I have now 1K, 560, 100.. -Toroid 12 turns and 20 turns -LEDs! -Batteries! Can anyone tell me what to do to run at least 10 LEDs with good or full brightness?

Question by jaesungauzakim   |  last reply