Introduction: Making a Simple Joule Thief (made Easy)

Picture of Making a Simple Joule Thief (made Easy)
Today I am showing you how to make a very simple joule thief. A joule thief has many applications, the best gadget that I made with was a "Water Powered Lamp", soon I'm going to post on a guide about it but first I need to post this guide. I used an iPhone 4S as my camera :))) 

What Is A Joule Thief ?

To simplify everything, a "joule thief" is a circuit that helps drive an LED light even though your power supply is low. What can we do with it? We can use it to squeeze the life out of our old, almost drained, non functioning batteries. This project can also be considered as a green and environmental experiment, we can also use it as a flashlight that can be ran by an old, weak, almost drained battery. I even tried to use my water powered battery from my previous instructable the "Water Powered Calculator", the project was featured and displayed in instructable's front page in the "Technologies" category.

My Next Projects That Involves A Joule Thief: (soon to be posted)
- Water Powered Lamp
- Water Powered Flash Light
- Dead Battery Drainer Lamp


Here's A Video From Make Magazine:

Step 1: Parts and Materials

Picture of Parts and Materials

The Parts Needed Are: (click the item to know where to find/ buy)

- Round Ferrite Toroid (can be found in old CFL bulbs)
- Old/ Used Batteries (can be found in garbage cans)
- NPN Transistor (2N3904)
- 1K Resistor (BRN-BLK-RED)
- LED Light
- Battery Tester (optional)
- Soldering Lead
- Copper Wire/ Magnet Wire
- Battery Case/ Holder

I want to share something. Here in the Philippines electronic parts are extremely cheap, they are extremely far cheaper from
radio shack, for example one transistor costs (2 phil. pesos - 6 US cents), a LED cost (9 phil. peso -  29 US cents) and a 1K resistor cost (25 phil. cents - 0.8 US cents). I usually buy thing from Deeco or Alexan. Usually prices here are 15x cheaper from radio shack. Price conversion - $1 US Dollar = P0.31 Philippine Peso (12/24/11). 

Step 2: Schematic Diagrams

Picture of Schematic Diagrams

Here are the schematic diagrams that are involved with the joule thief circuit.

Step 3: Winding Wire at the Toroid

Picture of Winding Wire at the Toroid

First, connect both ends of the copper wire before wounding, be sure to remove the insulation. Then try to solder the ends so it would not split up. Second, wind the wire until you run out of space in the round ferrite toroid. I have some tips for you, try to use a gauge #22 enamel coated copper wire for better performance, oh! my last tip is that "the more you wind the wire to the ferrite toroid the better".

Step 4: Soldering the Resistor

Picture of Soldering the Resistor

Solder the resistor with one end of the wounded ferrite toroid's wire. Oh! also don't forget to level the other end of the resistor with the other unused wire from the wounded ferrite toroid.

Step 5: Soldering the Transistor

Picture of Soldering the Transistor

Solder the proper connections to the transistor. For the emitter - connect another wire, the wire will be connected to the negative part of the battery. For the base - solder the other end of the resistor to the base. For the Collector Solder the unused wire of the ferrite toroid.

Step 6: Soldering the LED

Picture of Soldering the LED

Solder the shorter wire of the LED to the tansistor's emitter and the longer part of the LED to the transistor's collector. After all that, you can now trim the excess wires.

Step 7: Time to Look for Old Batteries

Picture of Time to Look for Old Batteries

Use your battery tester to confirm that your battery is close to death. The tester is only an optional tool, it's just used to determine the battery's remaining power.

Step 8: Time to Test It - You're Done !!

Picture of Time to Test It - You're Done !!

The wire connected to the transistor's emitter should be connected to the battery's negative side and the remaining wire of the ferrite toroid should be connected to the battery's positive side. Oh! one more thing, I advise everyone to use a battery case or attach a conductive magnet for each wire, so you wouldn't hold it all the time.


grimdaddy (author)2012-01-02

I am not a electronics guy and I have a few questions.
1:What happens if you hook this up to a new battery?
2: What happens if you hook it up to a three volt cell?
3:Could this be adapted to a 1watt Led that runs on six volts?
4: Could this be adapted to a flashlight, more specifically a tactical flashlight?
This looks like an idea that could go places.

chuckr44 (author)grimdaddy2016-11-07

There are pre-made dc-dc step-up convertors with a USB port already on them. Try this one: Input voltage is 0.9v to 5v, output is 5vdc. Easy peasy.

ASCAS (author)grimdaddy2012-01-02

1. It will have a longer battery life
2. The LED would wear out/burn
3. this circuit is not designed for that/ there are other circuits for that.
4. Yes. I made a flashlight out of it.
Good luck :))))

DrSurinderK (author)ASCAS2016-10-29

I have the topic as my school project but the problem is that the project looks too small. is there any way to make to big.

Nyxius (author)ASCAS2015-12-24

Actually if you added a capacitor in parallel with the transistor you probably could power a 6 volt device. But the pulse width would probably be so small it would still appear to be turned off.

Nyxius (author)Nyxius2015-12-24

Actually scratch that, you'd need to use a zener diode. To power higher voltages you need higher frequencies. This means lower switching potential is needed, and a lower capacitance. Lower capacitance than a diode is a tough one.

vmars316 (author)2012-01-03

Very cool project.
I am just learning about electronics:
could this same 'circuit type' be used for a
"free energy" from radio waves project?
Could someone, more qualified than me, design such a circuit?

ASCAS (author)vmars3162012-01-04

Harnessing radio-wave frequency and turning it into electricity is not that efficient.
Good luck! One of my first projects in electronics was the joule thief, since it is easy to construct.

richarno (author)2012-01-02

You got my vote!
Thanks for this nice instructable.

project_builder (author)2012-01-01

great project! Always wondering what to do with the old batteries i had laying around. im glad im not the only 13 year old doing projects like this. Try my 12 volt varyable power supply project! Thanks!

oanderson (author)2011-12-24

Nice Instructable, very useful for the novices out there and the more advanced tinkerers! I see your next project is a lamp, I check this one out: I'm thinking of making one :)

ASCAS (author)oanderson2011-12-24

thanks for the comment and reply :)))) Hope you luck :D

AndrewH345 (author)2017-06-24

can the wires be aluminium?

dfazio (author)2017-01-03

Hi Nice project.......

I am not from an electronics background, but I am wondering if this could be used to power a string of LED Christmas lights.

I guess you would need to use a fresh battery and change or add some components to up the voltage.

I am looking at a very simple circuit, this looks like it may do it, I would be interested in your thoughts

Thanks again

icehoney (author)2016-12-03

Is it possible to use conductive tape instead of wires to make it more compact? Or does it HAVE to be the copper wires?
Just wondering so I could make it sturdier and more compact.
Love this idea!

chuckr44 (author)2016-11-07

On one of your pictures near the top of this 'ible it looks like a circuit with a pre-made joule thief on it. Do joule thieves come pre-made? I'm having trouble finding spare parts to make one. I just don't have a lot of parts laying around.

sbagg (author)2016-10-18

does the copper wire have to be coated?

andrea biffi (author)sbagg2016-10-23

usually copper wire made for transformers has a transparent isolation layer

andrea biffi (author)2016-10-23

well done! I love your instructables! :)

WojciechF1 (author)2016-10-14

Thx ;) .

kavish laxkar (author)2016-05-16

Will it work with the transistor BC 547 NPN?
Plz help

WojciechF1 (author)kavish laxkar2016-10-14

Hi . It will , but you have to check the position of pins .

WillemNL (author)2016-09-29

what a great gadget!

FrancisT22 (author)2016-08-17

What should be the polarity output of the toroid winding?

ajay_1558 made it! (author)2016-05-23

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!

FrancisT22 (author)ajay_15582016-08-09

Sir, you wrongly connected the yellow wire, that should connect to the other side.

Raphango (author)2016-05-06

Nice! =D

6teeth (author)2016-01-22

Very nice.Ty.

Trying to google joule thief in denmark no result.:)

Nyxius (author)2015-12-24

This works by creating a crude RLC circuit. When the magnetic field from the inductor (choke) collapses, it creates a spike in the voltage that is just enough to power the LED. The transistor functions as a sort of one way capacitor. It acts as a capacitor when the current flows one way, and as a dead short when it flows the other way. It is a clever device. One could tune the relationship between the two for different joule sources. Tuning would make the conversion much more efficient.

dagob (author)2011-12-29

Can someone explain the theory behind this circuit?
Is it applicable to 9,6V? I know the circuit must be reconfigured for 9,6v usage, but if it is possible, could someone point out here how to do it?

Gary Viveiros (author)dagob2012-01-02

The circuit is an oscillator - specifically, a transistor,Colpitts oscillator. If you look at the classic Colpitts oscillator circuit you may ask," Where are the capacitors?" "Nowhere in this instructable does our brother mention any need for capacitors." There is capacitance. It is the capacitance between the wires that are being close, and tight-wound over the ferrite core. Remember, two things: first, a standard, passive capacitor is merely two conductors in a circuit separated by a non-conductor - be it air, mica, polystyrene, polycarbonate, or air or a vacuum- in this case, the insulation of the copper wires; secondly, an oscillator oscillates at a frequency determined by its' passive components, so even if you may think that this capacitance is so small that your capacitor meter isn't even registering it, you can figure that this circuit is oscillating at a very high frequency, and doesn't need much capacitance. That is why the author said that if you wind more turns on the coil it seems to get better. This is because the frequency is coming down into a more manageable range for the transistor, and there is a more optimum storage of power in the increased windings of the coil. This circuit is being operated as a flyback transformer in a boost configuration, meaning that the voltage of the weak battery is being augmented by the back-EMF (high spike voltage) from the energy stored in one-half of the two coils that are wound on the ferrite as the transistor oscillates. Well, where is the diode as are used in other flyback transformers? It is the LED, which is a lossy diode in the sense that it doesn't supply power to some other circuit, but uses all the available power itself to waste as a micro amount of heat, and to convert into light energy. Of course, without a measure of the inductance of the coils, you're blindly ignoring the maximum operating characteristics of the LED and transistor. Does the circuit work? Clearly , yes. May the output voltage be too much for the LED, or exceed the transistor's specs? It might. When you have properly made circuits, you just follow a recipe and do what it says, and it pretty much works. If you want to learn something, research the specs of the transistor you're using, and the formulas that govern the operation of the Colpitts oscillator, and you may find that along with an oacilloscope, you may find that you may have to adjust or add components to make everything last a long time. If you are a scrounger and can't get the transistor from your junkbox to work, learn how to identify an NPN from a PNP with a meter, and for your particular transistor, how to identify the Emitter, Base, and Collector. The wrong hookup will either cook the transistor or just not oscillate. An oscillator is just an amplifier with feedback, so if it doesn't oscillate, you may have to adjust the resistor. Don't give up if it doesn't work. You don't learn anything, if everything is given to you and you don't have to exert research and sweat to gain better understanding of what you're doing.

SirCubes (author)Gary Viveiros2015-12-24

AWESOME Reply...Thanx the some detail on how this works, It will help many others to understand.

MolecularD made it! (author)Gary Viveiros2015-09-17

Yup, an oscillator it is. Here is mine, as the first breadboard
prototype using a recycled S8050 transistor and a ferrite ring from
Amazon. From a new 1.5V AAA battery it oscillates between 280 mV and
3.94V at 570 kHz!

MolecularD (author)MolecularD2015-10-28

The yellow toroid above was made of iron, thus the high frequency of oscillations. With a better ferrite coil the frequency went down to about 33 kHz, which improved performance, as Gary suggested it would.

bartojohn20 (author)2015-11-08

does not boost voltage!

bartojohn20 (author)2015-11-08

i had made a joulthief. but it does to boost the voltage.

sabdul azeez abba made it! (author)2015-08-16

here us my own

Warmtint (author)2013-02-15

You need to improve your English. Thank God for the pics because the written instructions are nothing but confusing and impossible

Inlove (author)Warmtint2015-05-14

Kindness goes a long way. Thanks ASCAS.

ASCAS (author)Warmtint2013-02-16

I'l try my best to re-update my words/ instructions. Thanks though, for reminding me. It was a challenge for me to write ible guides since I posted this when i was 11 and English isn't my primary language.

PhilKE3FL (author)ASCAS2014-01-14

I think you did a very good job. It was obvious English was not your native language as it would be for me if I tried to write an Instructable in German. I even lived and went to university there for a year when I was in my early 20's but now I'm in my 60's and it has been a very long time since I've written or spoken German. At age 11 I think you've done an outstanding job! Updating the instructions, as your English improves, would be big help for, and I'm sure appreciated by, those for whom electronics isn't all that familiar.

AbhishekK1 (author)2015-05-07

what if the toroid core is magnetic, will it still work? Also, by using it to generate electricity to light up a led brightly, will it not cause the cell to deplete faster?

anuragtheviper (author)2015-03-04

will a BC 547 or 557 will work?

and if not in which item i can find a 2n3904

larry.rivard made it! (author)2015-01-14

made it.

larry.rivard made it! (author)2015-01-02

I made it on a breadboard. I found the toroid in a retired network switch power supply. I wrapped the toroid with 22 gauge solid wire. This is a great project and instructable. I will post it finished once soldered.

shaldar2 (author)2014-07-17

can anyone please tell me the problem i have used bc337 transister i have used bx547 kn2222A as well but it didn't worked out please help me where i am going wrong

kentuski (author)shaldar22014-12-26

you should connect the beginning and the end of the other wire

kentuski (author)shaldar22014-12-26

you have a wrong polarity of wire,,,

shaldar2 (author)shaldar22014-07-17

* BC547 correction

About This Instructable




Bio: Hi I'm Angelo! I am a 18 y/o college sophomore taking my majors in BS-ECE at the DLSU. I use my course as ... More »
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