How to Make a Joule Thief




Introduction: How to Make a Joule Thief

In this post I will show you how to make a Jouel Thief

Step 1: Components That You Will Need

Any NPN transistor, in my case 2N2222

Toroid Core

1K (1 kilo ohm) resistor

about 20-30cm of coper wire

LED in my case WHITE LED 3,3V 0,5W or any other

Little bit solder

Battery 1,5v

Step 2: Assembly and Connecting

Step 3: Coiling a Toroid Core

Step 4: Finished Projects

I managed, after 20 attempts to make this scheme

But it's working

Learn from mistakes

Step 5: Schematics

Step 6: And a Few Scematics to Play

Step 7: Video of This Project

See my video

And do not forget to subscribe on to my channel

Thanks for reading and watching

Link of video----Video

And link of my Youtube channel-----My channel

This project is supported by----Dzefri

Check out my other projects---My order project

2 People Made This Project!


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17 Discussions

Torrid coils wreak havoc on transistors."Big Clive" states to use a ferrite Vanilla bead coil as others will loose efficiency! This might have led to the non-working circuits.Also instruction on using a Heat Sink Tool when soldering any L.E.D. saving damage to the led/transistor. I myself have fried many of full legged leds from not protecting it with some type of heat sink device . Mine in pictures below.

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The Joule thief circuit in various forms is used to power things that require more voltage than you have available. Thus a "dead" 1.5 Volt battery at ~ 1 Volt can run an Ultra bright LED for days making a very nice little flash light. Been there done it. It can also be used to run other devices that require ~ 3V from a 1V battery adding a few more parts to filter the voltage and make it more DC. Look up my web page for additional links to such articles by others.

Not enirely positive, but I think this is to convert power into higher voltage to power a device like an led. leds are generally 2v-2.5v so one alkaline @ 1.5v battery can't overcome the internal resistance of the led at 2.5v, this increases the voltage over 2.5 to overcome led resistance. This will decrease the amperage in the circuit, but the battery has more than enough available to give so it isn't an issue.

How it works I don't know, maybe internal series wiring to make it 1.5v + 1.5v? Can someone explain the why and if I am correct?

There are many site to explain how this works but you can look at the experiments I've done on my site and how to make a simple Joule Thief more efficient, uses less current and from batteries even below 0.5Volts

I have many links & the first one is to a Wiki article explaining the joule thief circuit.


The 2,5V of the LED isn't any "internal resistance". It is the junction voltage that all semiconductor diodes have to pass and allow the current to cross the PN junction (the joint where the "P" and "N" semiconductors meet), and it varies according to the elements and doping used to create the semiconductor itself. This is why a germanium diode conducts at only 0.47 VDC and silicon diode conduct at 0.68 VDC. Light Emitting Diodes use different elements and doping for each color, so its PN junction can be as low as 1.7 VDC and as high as 4.5 VDC.

How it works --》

It's an easy "toy" circuit to demonstrate an electronics principle - and it can even be useful for producing a small amount of light from a "dead" battery - a joule thief will keep running right the way down to about 0.35V!

The original Joule Thief was created by Clive "Big Clive" Mitchell - he has a page on it here - - and a YouTube video demonstrating its creation here:

But there have been plenty of variations on it since he initially named it :)

Great joule thief circuit! This is great for sucking out the last juice in a battery!

Very nice, more info than most. I'm interested in the one that uses a 9V battery. What I have found is that no circuit is needed if the 9V battery is ~ 5V or less simply put the diode across it. Most ultra bright white LEDs are designed to work with 3V and will turn on ~ 2.5 or a bit less.

You can see my experiments on my web site & I also explain how to pass the "simple" joule thief and make a more efficient version that uses less current so even you dead battery will last longer.

My site is: and just click on the "Feature Article" link on that page. Then look for the, "Joule Thief Experiments" link.

1 reply