Supercapacitor Joule Thief




Introduction: Supercapacitor Joule Thief

Awesome Electronics Tutorials, Projects and How To´s

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!

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!

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!

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:



    • Tiny Home Contest

      Tiny Home Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Fix It! Contest

      Fix It! Contest

    41 Discussions

    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.

    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?

    1 reply

    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

    cool and super simple

    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?

    2 replies

    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

    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.

    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).


    1 reply

    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.

    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

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

    1 reply

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

    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

    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

    3 replies

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

    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

    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.

    -Bom trabalho, sua didática é perfeita.

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

    Forte abraço.


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