Making a Simple Joule Thief

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http://www.instructables.com/id/Making-A-Simple-Joule-Thief-made-easy/?ALLSTEPSMaking A Simple Joule Thief (made easy)

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HYPERLINK "http://www.instructables.com/member/ASCAS/" \o "view ASCAS's profile" ASCAS

HYPERLINK "http://www.instructables.com/id/Making-A-Simple-Joule-Thief-made-easy/?ALLSTEPS" \o "view ASCAS's website" \t "_blank" (I don't have)I got interested in electronics and mechanics when i was 4 year old. And started soldering circuits (kits) at 7 years old. And improved soldering at 9 years old without any kit only followng circuit...

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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 FromMake Magazine:

Step 1Parts 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

Iwant to share something. Here in the Philippines electronic parts are extremely cheap, they are extremely far cheaper fromradio 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 2Schematic Diagrams

Here are the schematic diagrams that are involvedwith the joule thief circuit.

Step 3Winding 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 agauge #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 4Soldering 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 5Soldering 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 6Soldering 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 7Time 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 todeterminethe battery's remaining power.

Step 8Time To Test It - You're Done !!

Dec 24, 2011. 2:29 PM

HYPERLINK "http://www.instructables.com/member/ASCAS/" ASCAS(author) says:

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

1

Jan 1, 2012. 4:39 PMproject_buildersays:

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!

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Jan 2, 2012. 7:12 AMricharnosays:

You got my vote!Thanks for this nice instructable.

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Jan 2, 2012. 12:49 PMgrimdaddysays:

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.

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Jan 2, 2012. 4:45 PM


1. It will have a longer battery life2. The LED would wear out/burn3. this circuit is not designed for that/ there are other circuits for that.4. Yes. I made a flashlight out of it.Good luck :))))

Jan 3, 2012. 5:12 AMAce Frahmsays:

http://en.wikipedia.org/wiki/Joule_thiefReply

Jan 3, 2012. 4:51 AMLo-couksays:

Is there a practical use for a joule thief? Lighting LED's with a flat AA battery isn't the best use, so I'm wondering if it can be scaled up to start a car with a flat battery etc..

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Jan 2, 2012. 11:19 PMDick Cappelssays:

If I may, I would like to suggest a site that discusses alternative construction and components, and has tips on how to get your joule thief running,

http://cappels.org/dproj/ledpage/leddrv.htm

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Dec 25, 2011. 10:59 AMacmefixersays:

The better choice for a Joule Thief is the 2N4401 or PN2222A, the 2N3904 is a poor choice.

I think I've said that dozens if not hundreds of times, and it seems to me the more I say it, the more people use this weakling transistor. It seems like what I say has the opposite result. Maybe I should start using reverse psychology. Maybe if I start telling everyone they should use the 2N3904 because it's the best, they'll do the opposite and quit using it. Then when they find out how much better the other transistors are, they'll realize how weak the 2N3904 is. But for some reason I keep on being an optimist and tell people the truth, and, well, you know the story.

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Dec 25, 2011. 4:16 PMhanelypsays:

I've had good luck using the 2N3904, or 2N3906 with polarity reversed. But I also parallel the resistor with a small capacitor (a couple pF is good) which helps the transistor turn off a lot faster, which helps performance whatever transistor you use. Also, if you use a 2N3904 with a full alkaline cell, a 2k resistor is appropriate to avoid exceeding transistor specs.

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Dec 25, 2011. 9:40 PMacmefixersays:

I'm shocked. You're the first to use the words transistor specs, not to mention avoid exceeding. All of the people who experiment with (more like abuse) transistors, as far as I can tell, don't even know what a datasheet is. Their projects have to be fed a constant diet of replacement transistors. Thanks for restoring my faith in humanity. Back to JTs. I foundthis document, and I find it interesting that the author finds that adding the Schottky diode increases the Figure of merit. I'll have to do some experimenting to find out why this occurs.

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Jan 2, 2012. 2:19 PMcvbrittonsays:

If I understand the Schottky diode correctly, it has a very low turn-on voltage (in the forward direction) which will let the positive pulse start sending current into the capacitor where it accumulates until the LED turn-on voltage is reached. When the pulse goes negative there will still be some usable charge in the capacitor that would otherwise be dumped to ground. Sound reasonable? Anybody got a spice model to run?

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Jan 2, 2012. 11:13 AMaschmidt7says:

The thing I like about this is the blue light indicating the jewel thief action is kinda hard to see. If it was RED the whole world would see whats going on with your toy

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Jan 2, 2012. 11:08 AMsgoldbergsays:

Very nice work and excellent pictures and explanations.keep it up!

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Dec 30, 2011. 8:28 AMactivenowheresays:

Can you link to a place selling suitable toroid? Taking apart a CFL really isn't the best option for me.

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Jan 2, 2012. 10:44 AMCanoemansays:

Any ham radio store or electronics shop should carry a wide spectrum of toroidial cores.

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Jan 2, 2012. 7:51 AMzappymaxsays:

eventually when you discard old lamps or circuitry, keep some of the toroids...

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Jan 1, 2012. 7:12 PM


radioshack

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Dec 27, 2011. 7:46 AMbuild-matsays:

It very much impresses. But there are questions. Esteem also here these articles:http://www.build-mat.ruToo it is a lot of interesting.

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Dec 27, 2011. 2:52 PM


Sorry. But I don't know that language.

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Jan 2, 2012. 9:46 AMlegomitch02says:

http://translate.google.com/translate?sl=auto&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.build-mat.ru%2F&act=url

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Jan 2, 2012. 9:35 AMhairybaroquesays:

At the risk of showing abysmal ignorance, I didn't know what CFL bulbs were, (Thank you, Wiki) so could I just add that, for people like me, CFL means Compact Fluorescent Lamp. How very nice to find that parts of them can actually be useful!

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Jan 2, 2012. 9:05 AMnetrunner38301says:

would be nice to see an instructable that takes an old battery and drains it into a storage trap of some sort that could be used to recharge the batteries that can handle a recharge using a similar process to the joule thief

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Dec 29, 2011. 8:22 AMdagobsays:

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?

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Jan 2, 2012. 8:09 AMGary Viveirossays:

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.

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Dec 26, 2011. 2:48 PMMr Sinstersays:

Yes I understand the fundamentals of resistors for I had already build like 3 but what i was wondering is can you use a fresh battery instead of a drain battery? For i think that a fresh battery will probably drain out or something.

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Dec 26, 2011. 6:54 PM


Yes. You can use a fresh battery. I've tested it and it will have a longer time lighting the joule thief compared to the old one.

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Dec 26, 2011. 2:41 AMkostyasays:

I've built a dozen of flashlights around this schematic using BC547 as an NPN transistor. They work well but efficiency is low. If electronic parts are so cheap in the Phillippines you may try to buy Zetex LED drivers. They are a bit tricky to solder being smd-components but adding a ready-made inductor and a resistor you will have a highly-effective flashlight.

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Dec 26, 2011. 4:12 AM


Its true. But I am teaching the other people, mostly the beginners, to learn more in a slow instructional process :\\

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Dec 24, 2011. 4:59 PMbigjeff5says:

It's winding, not wounding. To wound the toroid you'd need to hurt it in some way, and I don't think such a thing is actually possible for an inanimate object.

Yes, the toroid is wound, but you had to wind it to make it wound, you didn't wound it. If this is incredibly confusing, this should help clarify things: wound, the past tense of wind; and wound, the act of injuring, are homographs. They are spelled the same but pronounced differently, and have two entirely different meanings. They aren't even the same tense.

Wind and Winding are the words you want here, not wound and wounding.

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Dec 24, 2011. 5:08 PM


I'm sorry I did that 12:00 midnight waiting for Christmas, my brain seems to be dull :)))) I'm so sleepy. Don't worry I'l change that.

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Dec 24, 2011. 11:11 PMsouichisays:

isnt 1us$ = 50 philippine peso? but then this comming time it becomes P43

and yes electronic stores here in the philippines is very cheap i make alot of projects with electronics..

nice instructables.

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Dec 25, 2011. 12:52 AM


Yesterday, I was shocked because the conversion was around 1us$ = 31 php.

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Dec 25, 2011. 11:58 AMacmefixersays:

A good point to start is at least 10 turns. But when you wind more than a few feet ( or a meter or more) of wire onto a core, the DC resistance of the wire begins to waste energy and cause a loss of efficiency.

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Dec 25, 2011. 4:20 PM


Thats true :))

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Dec 24, 2011. 5:20 PMicekidsays:

I see you made another project of yours! I already made a joule thief but it gave me a hard time making it because some guides in the net are incomplete but yours is extremely complete and fully illustrated.

Keep it Up! Nice work!I find subscribing with you very useful. Thanks a lot with your cool projects.

Joule thief

From Wikipedia, the free encyclopedia

This articleneeds additionalcitationsforverification. Please helpimprove this articleby adding citations toreliable sources. Unsourced material may bechallengedandremoved.(January 2011)

A joule thief on a breadboard, driving a red LED from 0.5 V input. This circuit uses the magnetic coupling between two chokes to drive the transistor. It is a shoddy and unacceptable way to make a Joule Thief coil. See discussion for further info.

"Joule thief" is a nickname for aminimalistself-oscillatingvoltage boosterthat is small, low-cost, and easy-to-build; typically used for driving light loads. It can use nearly all of the energy in a single-cellelectric battery, even far below the voltage where other circuits consider the battery fully discharged (or "dead"). Hence the name suggests the notion that the circuit isstealingenergy or "Joules" from the source. The term is apunon the expression "jewelthief", one who stealsjewelryorgemstones.

The circuit uses the self-oscillating properties of theblocking oscillator, to form an unregulatedvoltage boost converter. As with all power conversion technology, no energy is actually created by the circuit. Instead, the output voltage is increased at the expense of higher current draw on the input. As a result, the amount of power entering the circuit is the same as the amount leaving, minus thelosses in the conversion process.

Contents

[hide] 1History 2Description of operation 3See also 4References 5External links

[edit]HistoryIn the November 1999 issue of Everyday Practical Electronics (EPE) a simple circuit was published by Z. Kaparnik that consisted of a transformer-feedback single-transistorvoltage converter. The Joule Thief circuit is based on the blocking oscillator, which uses a vacuum tube /thermionic valveand dates to prior toWorld War II.

[edit]Description of operation

Example of a joule thief circuit driving an LED. Thecoilconsists of a standardferrite toroid corewith two windings of 20 turns each using0.15 mm(0.006 inch) diameter wire(38swg)(34-35AWG). The circuit can utilize an input voltage down to about 0.35 V and can run for weeks using a1.5 VLR6/AA. The battery voltage is usually1.5 V. The resistor is~1 k,1/4 W. Thetransistorcould be a BC547B, 2SC2500, BC337, PN2222, 2N4401 or other NPN. Vceo= 30V, P = 0.625W. A whitelight-emitting diodewith Vf= 3.2V might be used.[1]

The waveform of an operating joule thief, showing a 30% duty cycle at approximately 40 KHz

The circuit works by rapidly switching the transistor. Initially, current enters the transistor base terminal (through the resistor and secondary winding), causing it to begin conducting collector current through the primary winding. This induces a voltage in the secondary winding (positive, because of the winding polarity, seedot convention) which turns the transistor on harder. This self-stoking/positive-feedback process almost instantly turns the transistor on as hard as possible (putting it in the saturation region), making the collector-emitter path look like essentially a closed switch (since VCEwill be only about 0.1 volts, assuming that the base current is high enough). With the primary winding effectively across the battery, the current increases at a rate proportional to the supply voltage divided by the inductance. Switch-off of the transistor takes place by different mechanisms dependent upon supply voltage.

The predominant mode of operation relies on the non-linearity of the inductor (this does not apply to air core coils). As the current ramps up it reaches a point, dependent upon the material and geometry of the core, where the ferrite saturates (the core may be made of material other than ferrite). The resulting magnetic field stops increasing and the current in the secondary winding is lost, depriving the transistor of base drive and the transistor starts to turn off. The magnetic field starts to collapse, driving current in the coil into the light emitting diode (raising the voltage until conduction occurs) and the reducing magnetic field induces a reverse current in the secondary, turning the transistor hard off.

At lower supply voltages a different mode of operation takes over: The gain of a transistor is not linear with VCE. At low supply voltages (typically 0.75v and below) the transistor requires a larger base current to maintain saturation as the collector current increases. Hence, when it reaches a critical collector current, the base drive available becomes insufficient and the transistor starts to pinch off and the previously described positive feedback action occurs turning it hard off.

To summarize, once the current in the coils stops increasing for any reason, the transistor goes into the cutoff region (and opens the collector-emitter "switch"). The magnetic field collapses, inducing however much voltage is necessary to make the load conduct, or for the secondary-winding current to find some other path.

When the field is back to zero, the whole sequence repeats; with the battery ramping-up the primary-winding current until the transistor switches on.

If the load on the circuit is very small the rate of rise and ultimate voltage at the collector is limited only by stray capacitances, and may rise to more than 100 times the supply voltage. For this reason, it is imperative that a load is always connected so that the transistor is not damaged. Note that, because VCEis mirrored back to the secondary, failure of the transistor due to a small load will occur through the reverse VBElimit for the transistor being exceeded (this occurs at a much lower value than VCEmax).

The transistor dissipates very little energy, even at high oscillating frequencies, because it spends most of its time in the fully on or fully off state, thus minimizing the switching losses.

The switching frequency in the example circuit opposite is about50 kHz. The light-emitting diode will blink at this rate, but thepersistenceof the human eye means that this will not be noticed.[1]The typical Joule Thief may draw around 80 milliamps at 1.5 volts, or 120 milliwatts. The output to the LED may be about 20 milliamps at 3.3 volts, or 66 milliwatts. The efficiency (power out divided by power in) of a typical conventional Joule Thief is in the 40 to 70 percent range (55 percent in the above case). The factors most affecting this are losses in the resistance of the coil wires, and losses in the transistor, mainly due to not being fully turned on during on time.

A simpleshunt-regulatorfor loads requiring a constant voltage

When a more constant output voltage is desired, avoltage regulatorcan be added to the output of the first schematic. In this example of a simpleshunt-regulator, a blocking diode ("D_rect") allows the secondary winding to charge a filter capacitor ("C_filter") but prevents the transistor from discharging the capacitor. AZener diode("Z1") is used to limit the maximum output voltage.

[edit]See also Flyback converter Boost converter[edit]References1. ^ab"Make a joule thief", www.bigclive.com, retrieved 22 December 2010

[edit]External links Joule Thief Simulation

Documents

Making a Simple Joule Thief