Introduction: Supercapacitor Joule Thief

Picture of Supercapacitor Joule Thief

In this project I will show you how I created a very popular and easy to build circuit, the joule thief, in order to power LEDs with voltages from 0.5V to 2.5V. This way less power from the used supercapacitor is unusable.

Step 1: Watch the Video!

The video should give you all the information you need to build your own joule thief. The next steps are just additional information to make your life easier.

Step 2: Order Your Parts!

Picture of Order Your Parts!

The circuit itself only requires 3 components. Here you can find links for all of them.

1kΩ or 2kΩ Resistor:

Ferrite Toroid Core:

Enameled copper wire:





1kΩ or 2kΩ Resistor:

Ferrite Toroid Core:

Enameled copper wire:




1kΩ or 2kΩ Resistor:

Ferrite Toroid Core:

Enameled copper wire:



Step 3: Build the Circuit!

Picture of Build the Circuit!

After you wound your transformer, the way it was demonstrated in the video, you only need to create 5 solder joints according to the schematic to connect the components to one another. Feel free to change the value of the base resistor like I demonstrated it in the video.

Step 4: Success!

Picture of Success!

You did it! You just created your own Joule Thief!

Feel free to check out my YouTube channel for more awesome projects:

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:


TravisM18 (author)2017-09-29

Try a bc517 Darlington transistor or avalanche transistor to get longer run time. Also 100k resistor, .01 or .01uf bypass capacitor. If you use Zenger diodes in with led it may cut current draw. Use super joule looper at also 8 ohm audio transformer on mini size should work.

PlasmaGuy101 (author)2017-03-16

Since germanium transistors have a saturation voltage of around 0.2 volts, 1/2 a volt less than an average silicon transistor's saturation point, could I use a germanium transistor in this circuit, and possibly light an LED from 200 millivolts?

UPDATE: I just found an old pnp germanium transistor and built a joule thief with it. (to use a pnp, just swap the polarity of the input and LED) With this setup I was able to light a white LED, albeit faintly, down to 0.23 volts

PruthiviT (author)2016-08-24

cool and super simple

kschmidt2 (author)2016-07-19

So, how do you charge it? And when do you know your Cap is at maximum capacity? I've got a 6.3V 4700uf that I'm connecting to a joule thief, but I only get about 3 seconds of power. How do you charge them?

GreatScottLab (author)kschmidt22016-07-20

The problem is that your 4.7mF cap can not supply energy for more than 3 seconds due to its low capacity. Try a supercap --> 1F-50F

kschmidt2 (author)GreatScottLab2016-07-21

Fair enough, so my touching it to charge is fine? And I've ordered a 22F cap, that seemed to work for you, so I'll stick with what works. I'm also going to try and add some form of universal charging system (Can charge multiple things other than this) that I can hook it up to. So I'll need to build a regulator (Planning a resistor and a Transistor inverter styled thing, so I'll work out the correct resistor so that when it hits a voltage that says it's full, the transistor stops flow. Could be interesting though. I'll see what happens.

mrc109 (author)2016-07-16

It is really fun to watch someone do something I wish I had the training to do and the brain to do it with! Don't say it is easy because I think it takes a special kind of brain to understand this kind of stuff, some kind of innate "talent" or the ability to grasp the math concepts that go along with knowing how to create and interpret your results. Are you Asian? It seems like Asian males tend to excel in mathematics, electronics, engineering, probably rocket science too, all the hard sciences stuff. It's got to be a genetic thing. Does anybody know if the genome of an asian male has a "smart gene" tucked away somewhere on the double helix? I think my double helix shares more of it's common traits with a chimpanzee, I have the furry arms and legs to prove it.

I have wondered if I could build my own super caps out of Coke can skins laminated between a dielectric? Does the foil in a cap have to be one continuous piece, or could I connect each layers band in series with a conductive strap between each successive layer? Is this a stupid idea? Like Forrest's daddy use to say "Stupid is as stupid does" (I always like to quote Forrest Gump whenever it applies to my ideas).


GreatScottLab (author)mrc1092016-07-17

I am German ;-)

goldenshuttle (author)2016-07-16

nice post, thumbs up..perhaps you can post on how to rewire DC motor for free energy next time. tip:add 2 more brushes on the armature, and change its coil winding.

KimS11 (author)2016-07-14

I'm gonna try it on a solar light...just have to dig up a supercap. I tried a 1.5v flashing led with one of the garden was a no-go

drj-research (author)2016-07-11

without checking the texts - looks like colpitts oscillator thus LED with 50% duty cycle , and back emf in inductor - feeds back to the capacitor

ac-dc (author)drj-research2016-07-14

Duty cycle to LED is buffered by supercap to effectively be near 100% duty the LED sees.

bassman1950 (author)2016-07-14

I made something similar and did not use any capacitor at all in my circuit

Just had a Torid a NPN general purpose transistor a 2k ohm base resistor a on/off slide switch a battery holder and a LED

My Torid had 8 turns one way and 4 turns the other way center tapped.

I used a base from a old garden solar light it had the battery holder and the switch and I used magnet wire to connect every thing with and it works like a champ

KimS11 (author)2016-07-14

Now someone just needs to make one with a solar cell in it, as well as a cap, then it truly would be free energy (if its close to the

DinoDen (author)KimS112016-07-14

The already make them in the form of those inexpensive garden solar lights.

KimS11 (author)DinoDen2016-07-14

YAH, they do...but with really evil Ni-Cad batteries in em. Plus the chip that is used to save power by modulating the light is really bad for anything other than a simple LED...not useful for much else

DinoDen (author)KimS112016-07-14

Well... the joule theifs output is switched as well. Not steady state.

But, you could try replacing the Ni-Cd battery with the super cap.

May work great and might have to give it a try.

gkist (author)2016-07-14

-Bom trabalho, sua didática é perfeita.

-Você escreve com a mão esquerda, esta tudo certo!

Forte abraço.


KimS11 (author)2016-07-14

I did forget to say, great circuit...well done instructions, simple and locical...effective. My hats off to you

Boulon (author)2016-07-14

Very good idea, simple and effective.

pskvorc (author)2016-07-14


sreeci (author)2016-07-14

Hello Scot,

I have always enjoyed, reading and understanding your projects.

When you explain the project, it is like an educational instruction. Well explained in such a way that may be understood by any one, even for a novice.

Thank you and please do more projects in the future.

By the way, I would like possess a Dual-Power-Supply DPS 5315, like you have.

I don't mind a used one. Please let me know.

KimS11 (author)2016-07-14

FINALLY someone is using a cap instead of a battery. First Indestructible that I'm actually going to take the time to make. Seems like Physical/electronic projects are limited unless you can afford a 3D printer.

panja5555 (author)2016-07-14

Wow lovly i too try

lapenta (author)2016-07-14

your channel is very good. Very detailed, well explained and illustrated. Thanks Great Scott for great videos and instructables.

lapenta (author)2016-07-14

your channel is very good. Very detailed, well explained and illustrated. Thanks Great Scott for great videos and instructables.

amariller (author)2016-07-12

Pretty cool!
I need a simple voltage regulator circuit. Maybe you can help.
I have a solar charger for my car cig lighter but it can over voltage. I thought about a 7812 biaed up to 13.2 (car battery charge V) but that's pretty sloppy. I need it to regulate then shut off if < min voltage. Got a simply circuit for me? Thx!!

wobbler (author)2016-07-12

Good Instructable and an interesting project. I've made many of these as emergency lights but not with supercaps. How long does the led stay on for?

Also, for anyone looking for a ferrite ring you can find them in old cfl lamps, as well as some other useful stuff. There's a good Instructable about it here:

DylanD581 (author)2016-07-11

Could this be done with a PNP transistor?

wobbler (author)DylanD5812016-07-12

Yes, just reverse the diode and the supercap when using a pnp.

abolfazl fakour (author)2016-07-11

verry good

jkelley2 (author)2016-07-11

Great video. Thanks!

I have a random question - what type of pen did you use in the video? The tip looks like a sharpie fine point pen, but the rest did not.

makeosaurus (author)2016-07-10

What does changing the value of the base resistor do?

reduces base current--> increases the charging time of the coil --> increases the overall frequency of the circuit --> makes it useable at 2.3-2.5V

DsCloak (author)GreatScottLab2016-07-11

One more thing. i have an interesting circuit for your PC is also powered by 9v, powers fan and chargers a 9v bat

DsCloak (author)GreatScottLab2016-07-11

@great scott
I have several improvements for this excellent circuit
and instructable. I'm a little hesitant to make instructables yet but id
be glad to give you the improvements. just link me. You game?

Hashem_Mehyar (author)2016-07-10

Hello Dr Scott, quick irrelevant question, how hard is making YouTube videos compared to instructables? personally, I found this instructable better than your video

ynneb (author)Hashem_Mehyar2016-07-11

We'll arrange for a full refund for you.

Making the video takes 30-50 hours. Writing a quick Instructables article takes 1 hour. But you really can't compare that because the video is part of the article.

Writing an instructable usualky takes me 6-12 hours, but 30-50 hours,,MAN !Thank you dude, i appreciate all the hard work you do.

About This Instructable




Bio: Awesome Electronics Tutorials, Projects and How To´s
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