Picture of Making A Simple Joule Thief (made easy)
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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). 
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vmars3163 years ago
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)  vmars3163 years ago
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.
grimdaddy3 years ago
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.
ASCAS (author)  grimdaddy3 years ago
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 :))))
richarno3 years ago
You got my vote!
Thanks for this nice instructable.
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!
oanderson3 years ago
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: http://www.instructables.com/id/Table-top-energy-seed/ I'm thinking of making one :)
ASCAS (author)  oanderson3 years ago
thanks for the comment and reply :)))) Hope you luck :D
sabdul azeez abba made it!11 days ago
here us my own
LeeamD1 month ago
LeeamD1 month ago
Warmtint2 years ago
You need to improve your English. Thank God for the pics because the written instructions are nothing but confusing and impossible
Inlove Warmtint3 months ago
Kindness goes a long way. Thanks ASCAS.
ASCAS (author)  Warmtint2 years ago
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.

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.

AbhishekK13 months ago

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?

will a BC 547 or 557 will work?

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

larry.rivard made it!7 months ago
made it.
larry.rivard made it!7 months ago
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.
shaldar21 year ago
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 shaldar28 months ago
you should connect the beginning and the end of the other wire
kentuski shaldar28 months ago
you have a wrong polarity of wire,,,
* BC547 correction
the polarity of the led is fine.
clchee made it!8 months ago

I couldn't get 2N3904 so I substitute it with 2N2222 instead and it works. My soldering isn't the prettiest but it works !

Check it out

MakersBox made it!10 months ago

I made a circuit board for it and added a switch. Makes a great night light. http://www.instructables.com/id/Easy-Joule-Thief-Soldering-Project/

ASCAS (author)  MakersBox9 months ago


moez.elmassry9 months ago
Can you post the circuit analysis? how does it work...
Thanks in advance
MFarrasalifm9 months ago

Hey, i saw the "mini version" do you have the instruction for that? i really need it. Thanks

rjohnson6510 months ago

Very simple design can use any "Common NPN type transistor" ie 2N3904, 2N2222, 2SC945, BC546, MPSA06...

But it would be slightly better with a 47uF cap across the battery...

10 to 100uF and 3 to whatever voltage... Size is the limit... really..


DangerousTim11 months ago


great job... but how that's work when the battery is death???

ASCAS (author)  mohammadsalem941 year ago

It depends on how drained it is. This circuit drains the battery completely to zero.

it's doesn't work. i use BC337 transistor? .

LAS1 year ago

On your schematic the coil has dots on opposite sides of the core, indicating that it is wound from opposite directions.

Your pictures show that you "double wound" the coil, starting both from same side.

To have the "double wound" pictures fit the Schematic, opposite ends of the "double wound" must be tied together, red from one end to black of other end :-)

PhilKE3FL1 year ago
What is the voltage drop for the LED I have two types 3V & 6V ultrabright LEDs will this work for them?
Would a 9011 transistor work in place?
It looks awesome... using this we can make a new 'radiation harvesting' system
syedj942 years ago
How much voltage is it outputting?
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