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

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). 
I am not a electronics guy and I have a few questions. <br>1:What happens if you hook this up to a new battery?<br>2: What happens if you hook it up to a three volt cell? <br>3:Could this be adapted to a 1watt Led that runs on six volts?<br>4: Could this be adapted to a flashlight, more specifically a tactical flashlight?<br>This looks like an idea that could go places.
1. It will have a longer battery life<br>2. The LED would wear out/burn<br>3. this circuit is not designed for that/ there are other circuits for that.<br>4. Yes. I made a flashlight out of it. <br>Good luck :))))
<p>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.</p>
<p>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.</p>
Very cool project.<br>I am just learning about electronics: <br>could this same 'circuit type' be used for a <br>&quot;free energy&quot; from radio waves project? <br>Could someone, more qualified than me, design such a circuit?<br>Thanks...Vernon
Harnessing radio-wave frequency and turning it into electricity is not that efficient.<br>Good luck! One of my first projects in electronics was the joule thief, since it is easy to construct.
You got my vote!<br>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!
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 :)
thanks for the comment and reply :)))) Hope you luck :D
<p>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!</p>
<p>hi<br>Will it work with the transistor BC 547 NPN?<br>Plz help</p>
<p>Nice! =D</p>
<p>Very nice.Ty.</p><p>Trying to google joule thief in denmark no result.:)</p>
<p>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.</p>
Can someone explain the theory behind this circuit?<br>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?<br>
The circuit is an oscillator - specifically, a transistor,Colpitts oscillator. If you look at the classic Colpitts oscillator circuit you may ask,&quot; Where are the capacitors?&quot; &quot;Nowhere in this instructable does our brother mention any need for capacitors.&quot; 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.
<p>AWESOME Reply...Thanx the some detail on how this works, It will help many others to understand.</p>
<p>Yup, an oscillator it is. Here is mine, as the first breadboard <br>prototype using a recycled S8050 transistor and a ferrite ring from <br>Amazon. From a new 1.5V AAA battery it oscillates between 280 mV and <br>3.94V at 570 kHz!</p>
<p>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.</p>
People have been using the ambguous phrase 'joule thief' which basically means nothing. In order to explain an ambiguously named circuit I tried to relate it to what has already existed for years in the common realm of electronics by means of the earliest use of a specific class of switching power supplies - the flyback transformer. As such, the flyback power supply would take the relatively low, full wave direct rectified line voltage of 164 VDC and add to it the output of the oscillating coil, rectified through a high-frequency power diode to minimize losses through the diode.This is how you got your 250 volt and higher plate voltages for tubes without having to have bulkier input power transformers. Of course the energy in a coil is stored in the magnetic field but it is unnecessarily splitting hairs to say that one must specify this for inductors, and yet if one discusses capacitors, you dont have to mention the electric field or the chemical composition of electrolyte for electrolytics, or the physical geometry of the plate effects in super capacitors. If further explanation is required, I wait for uncertainty to arise before addressing the concern further, otherwise the discussion could take the place of an instructable in itself. I would be interested in your analysis of the circuit, as to what you say the existing class of oscillator it is. An inductor is useless unless it stores and releases energy. To do this it has to cycle or oscillate at some frequency, and basically, 'it's all been done before&quot;. It has to fall in the class of some existing oscillator.<br>
<p>does not boost voltage!</p>
<p>i had made a joulthief. but it does to boost the voltage.</p>
here us my own
You need to improve your English. Thank God for the pics because the written instructions are nothing but confusing and impossible
Kindness goes a long way. Thanks ASCAS.
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.
<p>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.</p>
<p>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? </p>
<p>will a BC 547 or 557 will work?</p>
<p>and if not in which item i can find a 2n3904</p>
made it.
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.
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
you should connect the beginning and the end of the other wire
you have a wrong polarity of wire,,, <br>
* BC547 correction
the polarity of the led is fine.
<p>I couldn't get 2N3904 so I substitute it with 2N2222 instead and it works. My soldering isn't the prettiest but it works !</p><p><a href="http://www.instructables.com/id/1-Cell-Bottle-Illuminator-From-Scrap/" rel="nofollow">Check it out</a></p>
<p>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/ </p>
Can you post the circuit analysis? how does it work...<br>Thanks in advance
<p>Hey, i saw the &quot;mini version&quot; do you have the instruction for that? i really need it. Thanks </p>
<p>Very simple design can use any &quot;Common NPN type transistor&quot; ie 2N3904, 2N2222, 2SC945, BC546, MPSA06...</p><p>But it would be slightly better with a 47uF cap across the battery... </p><p>10 to 100uF and 3 to whatever voltage... Size is the limit... really..</p><p>Doc</p>
<p>great job... but how that's work when the battery is death??? </p>
<p>It depends on how drained it is. This circuit drains the battery completely to zero. </p>

About This Instructable




Bio: Hi I'm Angelo! I am a 17 y/o Physics Major at the DLSU and I use my course as an inspiration for making ... More »
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