Introduction: Joule Thief - Use LEDs With Only One AA Battery!

Picture of Joule Thief - Use LEDs With Only One AA Battery!

 Making LED devices portable can be a little bulky due to the batteries. The Joule Thief solves that, by boosting a single AA battery's voltage to a high enough level to light a LED.

This ible will entail how to solder a joule thief together from They cost $7 each.

The kit from thejoulethief is interesting in the fact that it deviates from the standard bulky joule thief design to a small and compact pcb layout with a few extra components for efficiency.

Step 1: Open Source

Picture of Open Source

Attached are the Eagle schematic and board files. 

Step 2: Gather Parts

Picture of Gather Parts

 Make sure you have all of the parts. Here is the listing:
 Qty 2. Transistor
2.2k resistor
Qty 2. 1k resistor
LED (your choice of color)
Qty 2. wire pieces

Step 3: Inductor

Picture of Inductor

 I first chose to put in the inductor. The inductor looks like a fat resistor. There is a spot on the PCB labeled "L1" where the inductor should go. 

Insert the inductor, bend the leads so that it says put, and solder it in.

Step 4: Resistors

Picture of Resistors

 Time for the resistors.
R1 is the 2.2k resistor (red red red).
R2 and R3 are the 1k resistors (brown black red)

Note that you should mount the resistors vertically to save space.

Insert, bend leads, and solder!

Step 5: Capacitor

Picture of Capacitor

 Grab the capacitor, insert in the spot labeled C1, bend and solder.

Step 6: Transistors

Picture of Transistors

 The next step is kind of tricky. The transistor leads are normally in line, however to insert them in the PCB you will need to bend the leads into a triangle shape (see picture).

After bending the leads, carefully push down the transistor into the pcb until it seats nicely. Solder.

Step 7: LED

Picture of LED

 The fun part! Put the LED in, make sure you note the orientation. The flat spot on the LED goes towards the flat spot on the silkscreen.

Step 8: Wire

Picture of Wire

 Here is the final step. Strip the wire ends, and solder it into the pads on the PCB.


Next it is time to test it out!

Step 9: Testing

Picture of Testing

The silkscreen marks which wire is positive and negative. Put the proper leads to any AA battery, dead or new, and see the LED light!

This is a great way to get compact LED lighting, using a minuscule circuit and one AA battery. The circuit operates off of "dead" AA batteries, making it a great way to reuse your old AAs. 

Pick up a kit at and have fun!


dudes (author)2014-04-27

I can't open eagle docs and I can't tell where to connect the input +/- or where the output+/- come from on the schematic provided. please help

vricsi94 (author)2012-07-25

Just a question before building it: What can I do if I want higher output voltage? Which part(s) should I change?

markb710 (author)2012-02-13

I'm not sure what program to use to open 2 Eagle schematic & board files. Can you please advise? Thanks Mark

Dave Kruschke (author)markb7102012-06-24

Now there is a new circuit out that uses only a tiny four legged IC, a tiny inductor, a battery and an LED. No toroids, transistors, resistors, etc are required with this "Joule Thief." Check out:
A simple schematic is provided...

Vator (author)2010-12-14

0.001 µF = 100 nF ?

rfmonaco (author)Vator2011-09-04

0.001 uf = 1 nf = 1000 pf

geeklord (author)2009-12-02

Finally! A kit! I could never get the toroid version to work. Just got little flashes.... Anywho, Ill have to get one of these.

highhacker (author)geeklord2011-01-26

I have wound Hundreds of torrois Jts hers one that will power a CFl blub or 500 christmas tree bulbs from just one 1.5 volt battery for 5 days straight !

shanakoenig (author)highhacker2011-07-17

Can you please post a schematic of this circuit?

pben (author)geeklord2010-10-23

I found a IC based boost regulator at Pololu that I liked. The circuit on this page uses 2N2222 which I haven't seen before. That will cause a loss in efficiency but should be a lot easier to find than the transistors of the classic Joule Thief.

mugiwara (author)2011-04-09

what inductance value is it?

microman171 (author)2009-11-19

Unless you are 'Big Clive'  I don't think you have permission to call the the 'joule thief'.  Big Clive was the one who coined this name.  Before he called it the 'joule thief' he called it the 'vampire torch'.

If you are Big Clive, thanks for designing such a nice kit!

Otherwise, please don't take names from other people's projects.

shams (author)microman1712010-12-16

Sorry dude BIG clive didnt patent joule we all can make and use it...thatz why inventor like big .c publishes this invention in public

highhacker (author)shams2011-01-26

It was patented In 2010 and the circuit described is not a Joule thief but a boost converted used in many solar garden lights . a REAL joule thief uses Ferrite bifialar transformer and ONE transistor and current draw is less than 1 milliamp on a silicon transistor of a volt of .725 . germanium Jt's can run as low as .2 volts and in the MICRO amp range while lighting up several Bright White Leds .

Sorry I did not know, but the Joule Thief may have been coined by Big Clive, but it seems like Evil Mad Scientist popularized it (with no mention of Big Clive). 

westfw (author)RazorConcepts2009-11-20

The EMSL does refer to Big Clive as "the original site"
Clive credits "Z. Kaparnik" in EPE magazine.  I suspect the origin lies even further away...  I don't think that anyone has trademarked the name...

This seems to be a different circuit, though (two transistors, single-winding inductor.)  Probably like or this one published (with lots of explanation) in Electronics Design

RazorConcepts (author)westfw2009-11-20

Can anyone reach Big Clive's web site about the joule thief? It doesn't work for me.

"In the November 1999 issue of EPE (Everyday Practical Electronics), a small and intriguing circuit was published in the Ingenuity Unlimited section by Z. Kaparnik. It was a very small implementation of a typical transformer feedback single transistor invertor. The transformer was a standard ferrite bead with two windings wound on it and the circuit was using the high voltage pulse generated when the transistor turns off to light an LED from a single 1.5V battery."

So it looks like it was way back in 1999 or earlier that this was invented.  The point I was trying to make is the kit name. 

Seeing as you have released all of the schematics for free, things are different.  You have every right to make and sell kits and boards.  Just make sure you put a link on your website for what a joule thief is (or rename it...).  Your circuit is actually different, so call it what you like!

highhacker (author)microman1712011-01-26

Actually the Circuit is a solar lightBoost oscillator circuit and not a joule thief ! and YEs Big Clives DID INVENT joule Thief . As the Name implys and Further more the Blocking oscillator was not invented transistorized until 1988 and the led was not invented until 1962 and available in red only . The actual product has many variations and we explored all of them from 2008 to 2011 . the Patent is issued in 2010 for Joule Thief whick used the ferrite transformer toroid and one transistor . We have versions that operate 1000+ white leds from less that 1 milliamp at 0.765 volts so what you are showing is an energy hog not a real joule thief that actually can do work . For more info and public Domain Circuits pertataining to modifications to a blocking oscillator invertor see overunity Dot Com and jule thief thread .

This link:

jomac_uk (author)microman1712010-12-10

So in the same vein, the people who invented the transistor, and the IC etc are the only ones allowed to use the name?

Just a point to ponder for the non pedantic of us out there

pedrotome (author)2010-08-10

I'm kind of an Eagle noob... How do you create/choose the "thing that goes on the Board design part" for vertical mounted resistors? Whenever I choose a resistor, it's always for horizontal mounting... Also, do you use a simplified library with only the most common components? If so, would you mind sharing it?, cause Eagle has lots of libraries and each library has lots of variations for the same component. For example, whenever I search for a resistor I'm like "HOLY -blam!- THERE'S SO MANY, WHICH ONE DO I CHOOSE!!?" and it just drives me mad... :p Finally, if I wanted to make this circuit to be able to power anything, would I just need to do this (see pic)? Also, is the input voltage/current irrelevant? The circuit will just boost whatever is inputed? Thanks! :)

yourdiyguy (author)2010-03-06

what is the v output of this device?

RazorConcepts (author)yourdiyguy2010-03-06

I'm not sure about peak voltage, but putting a 10uF cap on the output yields a roughly 2.1v  output. 

yourdiyguy (author)RazorConcepts2010-03-08

cool. I bought 4 so I could use them in some projects, also so I would not have to go through the trouble of getting all the bits and pieces. very excited!

Bongmaster (author)2009-11-20

any chance of all the component values? ;)

like wat the transistors are and wat kind of inductor :)

RazorConcepts (author)Bongmaster2009-11-20

I will post the schematics that will depict the values.
2x transistors are NPN 2222s, 3904s should work also.
I think the inductor is a 470uh, but anything from like 200-500 should work with varying efficiency.

Bongmaster (author)RazorConcepts2009-11-20

kool components that i actually have XD

TheWelfareWarrior (author)2009-11-19

BAH! I don't understand how the inductor works! WHYYYY!?!

(could someone post a link to something describing it?) 

404'd, and I understand how an inductor works, I guess I don't understand the way the circutry works together...

Isn't the idea of a joule theif to transform the low voltage of an almost dead battery into a slightly higher, more usable voltage?

Yup, that is what it does. See my response to atombomb1945

atombomb1945 (author)2009-11-19

So, the second transistor and the inductor would be what replaces the toroid?  Having very little knowledge of this, I am guessing that the inductor and the capacitor helps create the pulse that has the transistor drive the LED on low voltages.  (If I am wrong, please let me know as this site is for instruction)

Does anyone have a circuit diagram on this?

Basically the inductor holds the higher voltage charge, and the transistors/resistors/capacitor determine the switching frequency that switches between "charging" the inductor and discharging the inductor through the LED. 

AndyGadget (author)2009-11-19

Please add a circuit diagram to this.
Without it, it's just advertising spam.

RazorConcepts (author)AndyGadget2009-11-20

Check back tonight - I will put up the Eagle schematic and board files. 

AndyGadget (author)RazorConcepts2009-11-20

Great - Thanks.
It looks like a slightly different design to the usual, using only one winding.

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