Introduction: Cheap Voltage Regulated Joule Thief Power Supply/charger

Picture of Cheap Voltage Regulated Joule Thief Power Supply/charger

Maybe you know the very popular Joule Thief circuit, that usually is used to drive LEDs, but this instructable will show you how to regulate the output voltage up to 30 volts. You can regulate example to 5 volts that is enough to charge a phone or any USB device. It charges slowly but works. Or you can use as a power supply for an Arduino, or for a simple project too. It would be an useful device. I've made a few experiments before the creating the full circuit, so the circuit works fine. The circuit uses a zener diode regulate the output voltage. I will try to describe detalied because it is easy to make a mistake. Don't want to bore you with the working theory, but if you are interested read on wiki or watch this video. You can build this gadget almost free, can find most of the components in a CFL bulb, so let's begin.

Step 1: Tools and Materials

Picture of Tools and Materials


  1. soldering iron and of course solder
  2. a multimeter (optional)
  3. a wire cutter
  4. and.... that is all


  • You can see on the 2nd image that inside the CFL bulb is almost everything, you just need to buy a zener diode, wires and a PCB board. I've used components from a shop, beacause I can't make a clear instructable with short leg components
  • 2N2222 transistor or equivalent, on the transistor in the CFL writes 2222A
  • 47uF capacitor
  • 50-1k resistor
  • 1mm wire
  • USB female jack, if you want to make a charger
  • 1N4001 or any germanium diode
  • toroidal core from the CFL bulb
  • breadboard for testing (optional)
  • PCB board
  • zener diode with a value that you want to regulate the voltage We use the diode as a voltage regulator. Example I use a 5v1 (5.1 volts) zener that can regulate the voltage to about 5 volts that can charge a phone or can drive a Raspberry Pi. If you want to get another voltage example 7 volts for an Arduino, buy a 6v8 zener diode. If you're ready go choose your power supply!

Step 2: Choosing the Power Supply

Picture of Choosing the Power Supply

To operate the circuit you will need a power supply that have enough current to converting to voltage. If you want to operate can use 2 solar panels from old garen lights connected in paralell or use a small DC motor with a propeller on it. This can be used as a hydro or wind turbine. Don't be afraid, if you can't read the circuit diagramm, I will describe step by step the building, so go prototyping!

Step 3: Prototyping on Breadboard and Creating the Inductor

Picture of Prototyping on Breadboard and Creating the Inductor


  1. Get two wires, like on the first image and connect together, like on the second image.
  2. Now wrap the toroidal core with the wires and cut the endings, like on the third image.
  3. The starting of the green and red wires is named 1 and 2, and the and the endings are 3 and 4.
  4. Now solder the 2 and 3 together, like on the last image.
  5. And your inductor is done.


  1. Follow the images and the description, you can see the circuit with batteries on the 5th image.
  2. Put your transistor in the breadboard.
  3. Connect the resistor to the base of the transistor.
  4. After this put the soldered leg of the inductor in a free hole and connect to the positive wire of the battery.
  5. Connect the 1 and 4 legs of the inductor to the collector and to the resistor just like on the image.
  6. The negative wire is going to the emitter.
  7. Now you've made a simple Joule Thief, test it, if won't works check the connections. My 3v LED is working.
  8. If works get the cathode of the germanium diode, connect to the collector and put the anode in a free hole.
  9. With a capacitor connect the anode of the diode (positive) and the emitter (negative, GND).
  10. With reversed polarity install the zener diode.

Your protoype now is done! In the next step you can see the testing and the esplanation.

Step 4: Test and Explanation

Picture of Test and Explanation

The germanium diode blocks the current go backwards, and the capacitor with the zener diode ensure proper charging or flowing of the current. The zener's anode must be connected to the positive leg of the capacitor, that means reversed polarity. In this case the voltage is regulated to the zener's value (5v1). My multimeter showed me 5.17 volts, this is a perfect voltage for powering a project or for charging. If you solder anything in paralell to the zener's legs will works. In the next step i will make a USB charger, but you can connect example to an Arduion too.

Step 5: Soldering

Picture of Soldering

Simply solder the components together on a PCB. On the images is described everything you need to know. I think no need more explanation, so go testing!

Step 6: Last Test

Picture of Last Test

Plug your phone in and the charging starts. The ''dead'' battery can drive of course an LED, and if you connect this Joule Thief to a rechargeable battery will charge up in a few hours, you can save a lot of money if you use the ''zombie battery'' charger. Do not forget that is more better with green energy, like on the last image with the generator. Sorry for my potential English mistakes, hope you liked it, (vote on me) and hope you can use this instructable!


SwarT2 (author)2016-04-24

hello. i want to make a rechargeable circuit . The requirements are that it could be able to have a regulated voltage from 3-30 V in order to power up different type of devices and current is variable also. Plus, must be able to perform a overcharge protection at the same time not to spoil the battery .. Can you suggest me how do i start and all the requirements or maybe video for referrence pls ?

chuckr44 (author)SwarT22016-11-08

You could try a pre-made board <a href="">like this</a> on Ebay or Amazon.

امینل (author)2016-05-09

very gooood

FvadS (author)2016-04-20

How about output amp?

MakinThings (author)2016-01-07

Nice intructable. What would happen if I used an unstable DC source (solar \ turbine) and it went above the voltage I had it set to? Ex. If I have it set to 5v as you do, and for some reason the power coming in goes up to say 6v or even 12v?

JamesW262 (author)MakinThings2016-03-30

you can always add a 5v regulator to maintain your output(or input) when your input voltage spikes

MakinThings (author)JamesW2622016-03-30

mm I'd be scared that it's starting to compound losses....

JamesW262 (author)MakinThings2016-04-02

Why be scared, you can never make an omelet without breaking a few eggs figuratively speaking

Dota 2B (author)2016-01-13

Dude, i follow yours steps, but i only get 1,6v from a 1,25v battery, what could be wrong? The toroid may be?

JamesW262 (author)Dota 2B2016-03-30

yes more than likely, you may have twisted the wrong two wires very easy to do. say you have a red and black wire and you wound them on a toroid say 20 turns, you,ll have two wires on both sides, a red and black on side 1 and a red and black on side 2 take the black wire from side 2 and twist it to the red on side 1 and that,s your battery plus wire will go. here,s a you tube link that shows how to wire what i described hope this helps you out, and the efficiency of this or any joule thief is only limited by the toroid windings so experiment with the coil ratio find what works for you.

celalboz (author)2015-06-14

Good job young man. Do you know a way to ımprove thıs cırcuıt ın terms of output current such as by usıng a better transıstor or better terroid wıth more wındıngs or perhaps a bıgger capacıtors and maybe maybe dual transıstor paralel. I,ve made thıs but ı would lıke to charge 4 aa wıth 4v solar whıch needs 6v. thanks.

ArifSae (author)celalboz2016-03-07

\ :p

AnaM55 (author)2016-01-18

Just what i needed! I was given 4 old giant batteries, 2v at 600ah each. My whole solar panel setup lights and stuff is designed for 12v. I solved the charging using Renes re-emf charger that self regulates. However now i need a step up regulator for the output to my lamps and stuff. But i'm completely ignorant of elecronics, i can only follow schematics and assemble without having the slightes clue bout how it works. Is there any chance u could tell me the voltage and amperage ratings i should get for the components with my batteries? Pleaaaaaaaase!????

MakinThings (author)AnaM552016-02-04

your best bet would be to use a charge controller for solar panels. It will have the proper regulators all built in. Many are available on Amazon for cheap. If you need high power stuff (powering a house or otherwise), then you would need to get higher quality stuff.

fibn muhammad (author)2015-11-27

owesome...great job... i was looking for this component... cos it very expensive to me to buy a dc to dc converter :)... thanks a lot :)

harispark (author)2015-11-18

I use the circuit with free energy generator circuit for cell phone charger, the transistor burn. What reed

Jayson JhillB (author)2015-07-04

I changed the 5v zener to 12v and the 16V 47uF capacitor.. I managed to make it work(I get around 11.35V) but why does the voltage drop to 2.5v when a load is attached?? should I also change the rating of the capacitor used? Thanks!!

FokkoP (author)Jayson JhillB2015-07-29

The voltage drops to about 2.5V because your power supply (the battery or a solar panel) only delivers enough power for your project to run continuous on 2.5V. All that the diode does is make sure the voltage doesn't go over said forward voltage by redirecting it to ground when it does. This way you get small spikes that stop at the desired voltage. By instead using a capacitor at the end stage (which might actually also blow up the capacitor if it doesn't have a high enough rating, but that doesn't seem to be a problem in your case) you store the energy, but when adding a load you also instantly pass it (partially) through. The reason capacitors are used in power supply situations is to keep the voltage constantly high, not constantly low (in this instructable 5V)

psilord made it! (author)2015-07-01

I made this Joule thief, and it's not working correctly. I put a 1.5V AA battery in and I get 1.5V out. Can you please help? Thanks!

psilord made it! (author)2015-07-01

Please help!! I have tried building a joule thief, and when I put 1.5V in I get 1.5V out. I have tried different coils, without a resistor and with.. Same results.. Here's an image of my board. Thanks!

psilord (author)2015-07-01

Isfaaq (author)2015-05-02

i have been thinking about the toroidal thing... What if i replace it with a round magnet(from a speaker), what will be the consequences?

Imetomi (author)Isfaaq2015-05-02

Well, I don't know but you would try. Yoh can get toroidal inductors from cfl bulbs like me.

Isfaaq (author)Imetomi2015-06-10

I got a toroid... I'll try the magnet thing and let you know( maybe i'll make an Instructable on it)
I'm pretty sure it'll work, because the purpose of the toroid is only to concentrate the magnetic flux

KlineH (author)2015-05-05

I tried this and It works fine for me, a months ago i've been watching & read stuff about this juile thief it really caught my attention and make one the maximun output voltage was about 30 to 65 volts from a 1.5 volt alkaline battey with a 1 inch toriod wind 28 turns using 24G & 28g coil wire i tried different types of zener diode and capasitor for the output voltage which i will use to run a 12 volt motor.

SirJoeyme (author)2015-02-07

Finally! I've been looking for something like this. How long does it take to charge a phone with this? Would it be slower than normal?

Imetomi (author)SirJoeyme2015-02-07

Oh, and if use two 2 AA rechargeable batteries will be faster. I tested the current with my multimeter, and it was higher than 200mA. If you liked vote on this instructable in Make Energy and in the other contests.

celalboz (author)Imetomi2015-03-31

Young man, it is a fine job you did with this, I too have one now but I like to connect two AA to it, question is serial or parallel? 1.5v input or 3v or more , what is the max input? and with 3v what is the output before zener diode?

Imetomi (author)celalboz2015-03-31

Thanks, and works maximum only with 2 AA 1.2 volt batteries. So with a 2.4 volg inpug voltage. If you connect them in paralell the capacity will be higher. The output voltage without regulation is very high, may increase up to 70 volts for me, but with a very small current. The zener ensures optional current and voltage.

jpatel32 (author)Imetomi2015-02-16

I made it but not properly working. ...

Imetomi (author)jpatel322015-02-16

You can see on my multimeter and on my phone that's working. Maybe you reversed the zener polarity. In this cause the voltage will be about 0.9-1v. The anode is connected the negative output of the Joule Thief. Or check the connections. Maybe is wrong something with the capacitor.

Imetomi (author)SirJoeyme2015-02-07

Yes it charges slower than a wallplug, but if phone is turned off can charge 1 percent per 6-7 minutes on my 1700 mAh capacity battery. If your phone's capacity is smaller charges faster. Nice to helping for you.

jpatel32 (author)Imetomi2015-02-12

I have create 5v & 1A charger. ...
plz so me.....

-max- (author)jpatel322015-02-17

Use a 5V switch mode power supply. You can source the switching regulators, like the LM2596, and wire them up based off of the datasheet.

That regulator, however, is a buck converter. It takes higher voltages and steps it down to a tamer level. It can deliver up to 3A w/ heatsink, and there is a variant designed to deliver just 5V.

Imetomi (author)jpatel322015-02-12

Ok, congratulation, but this

Imetomi (author)Imetomi2015-02-12

isn't a charger, it's a regulated power supply that can charge phones. Originally wasn't designed for charging, I just used this for the example.

-max- (author)SirJoeyme2015-02-17

Much slower than normal. Many modern phones can draw over 3A over some USB wall chargers to charge fast! My Galaxy Note 3 charger is rated 5.3V & 2.5A. The reason it is overvolted by 0.3V is because they are trying to push the poor thin USB wires to their limits and by doing so, they had to do that to compensate for voltage sag from the resistance of the wire! LOL! A bit of a hacky solution, that is, samsung!

Anyway I did try to build a simple solar charger a while back using solar power, and ran into an issue that the phone actually uses more power when on than the charging speed is! (In fact, it kept beeping and buzzing because every time the phone starts accepting a charge, the voltage would sag too much and charging stops, voltage rises again, starts charging again, and you get the idea.) So I have to turn off the phone and let it charge ALL DAY in the window, and I still not get up to a full charge. 200mA is probably the short-circuit current, when the voltage output is nearly zero because it's shorted. At the 5V output rating, the output current is probably considerably less, although I have not made this specific circuit, so cant say for sure!

消磨好 (author)2015-02-28

im Chinese. what's the size of the charge电池?

Imetomi (author)消磨好2015-02-28

Without the phone 5v and about 300 mA and when I connect my phone is about 200-300mA.

-max- (author)2015-02-17

Well, actually, it just occured to me. that the joule thief is one of the simplest boost converters you can make!!! Look at the schematic for a boost converter here:

See the similarities?? Just replace that switch that appears to short the inductor to ground with the 2N2222, and just add another coil to switch the transistor ON and OFF based on the (change of) current flowing though that inductor, and just like that, a really basic boost converter!!!

To improve upon the design, get rid of that secondary coil, get a separate low power PWM oscillator, connected to the base of that transistor, and use a comparator or error amplifier to adjust the PWM duty cycle so as to regulate the output voltage! (so as the voltage gets too high, above a given 5V reference, the oscillator duty cycle is basically completly off, and as the voltage falls below that 5V ref, the oscillator duty cycle goes up to like 60% maximum) But by the time all that circuitry is developed, you might as well just buy an off-the-chelf solution :)

-max- (author)2015-02-17

Nice circuit! Very simple, although it's too bad you went with the shunt-regulator path :( It works OK for small power supplies, but the better topology would be a boost converter. Although that would require a bit more stuff to make work well. The advantage of a proper boost converter is that is will mostly be MUCH more efficient than this. That means more power from the solar panel, and more power extracted from the battery. Though for what it is, it's nice little thing! Good job!

Jan_Henrik (author)2015-02-08

that is a very poor voltage regulator circuit.

Imetomi (author)Jan_Henrik2015-02-08

And what is the problem with it? It works, and is almost free.

Jan_Henrik (author)Imetomi2015-02-10

Oh, I didnt mean that it is a bad one, its just poor, could be a better one :P

Imetomi (author)Jan_Henrik2015-02-10

Oh, sorry for misunderstanding, and I've looked your online gallery. It is very nice, what kind of camera are you using?

Jan_Henrik (author)Imetomi2015-02-11

Thank you! I´m using a canon eos 600D ( T3i rebel i guess ), i love canon cameras!

peabody1929 (author)2015-02-07

Consider: "DC-DC Converter Step Up Boost Module 1-5V to 5V 500mA USB Charger" on eBay for $1.49.

Imetomi (author)peabody19292015-02-07

Yes I know these converters, but my target it was to make a homemade, anc shoe you how to make.

discostu956 (author)2015-02-07

like this, cheers. Do you know what sort of current it's capable of delivering, or an easy way of controlling the current? Thinking of diving small led string off a single battery and want to make sure I want overdrive them

Imetomi (author)discostu9562015-02-07

If you want to control the current replace the 220 ohm with a 1k potentiometer.

About This Instructable




Bio: Hi, I'm Tamas (Thomas), a 17 years old Hungarian guy. My hobby started more than 10 years ago. I learn electronics, physics, programming, IoT ... More »
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