Introduction: Super Simple Inductor Joule Thief!

About: Tanmay Bhonsale a.k.a enceladus2000

Hey Everyone! In this Instructable I'll show you how to make your own simple inductor joule thief, in just under 10 minutes! This circuit is so simple, even those not familiar with electronics can try it out as their first project!

What is a Joule Thief?

A Joule Thief is a simple electronic circuit, that takes in a small input voltage (<2 volts) and multiplies that voltage to power devices that require higher voltages to run (like LEDs, that usually require at least 2-3 volts to run).

How is this Joule Thief different?

Unlike most other joule thief circuits, this circuit uses a standard inductor. Hence there is no need to salvage a toroid and wind wire away to glory.

The circuit is super simple, can easily be assembled on a breadboard, or can be soldered onto really tiny PCBs, if you want...

I have made a video, explaining all you need to know about a Joule Thief, along with the circuit and more... Check it out (try the HD option)...

BTW hope you liked the video's humour :P

Project Details:-

Time: <10 minutes (assembly on breadboard)

Cost: <$1

Difficulty: Easy

Requirements: Basic knowledge of electronics (newbies are welcome!)

Step 1: What Is a Joule Thief?

According to Wikipedia,

A joule thief is a minimalist self-oscillating voltage booster that is small, low-cost, and easy to build; typically used for driving light loads.

Didn't get it? That's no surprise- Wikipedia is renowned for defining the simplest of things with as many technical terms as possible, which they probably think may improve the reader's experience.

Fortunately there's a much simpler explanation, as shown in my video-

A joule thief is an electronic circuit that takes in a small voltage (like from a 1.5v AA battery) and turns it up to a higher voltage (to power devices like LEDs, which require 2-3volts to run). This circuit can power low current circuits, such as LEDs, buzzers etc. with a small voltage source, such as a 1.5V AA battery.

So, if you want to run a low power device with a compact power source that needs to last long, a Joule Thief and an AA battery is just what you need...

Step 2: Materials...

As the circuit is very simple, materials are easy to get. There is no need to salvage components from old stuff, unlike in the case of using a toroid... But if you really want, you may.

Materials(All materials can be got from RadioShack) :

  • LED - Any colour will do, however colours like green and blue work best
  • Transistors - 1 NPN (BC547) and 1 PNP (BC557)
  • Resistors - 1K ohm * 1 and 33K ohm * 1
  • Capacitor - 0.01uF ceramic capacitor
  • Inductor - Anything between 220uH and 510uH (I used 470uH)
  • Breadboard
  • AA battery - or any battery giving less than 1.5volts
  • Jumper wires

Step 3: Assemble the Circuit...

*I've included the circuit diagram. Check the last picture above...

The circuit is small enough to be done on a mini breadboard. I've used BC547 and BC 557 transistors. If you use other transistors, you may have to change the circuit on the breadboard a bit, as they may have different pinouts...

Step 4: Prepare AA Battery and Finish....

Of course, you can use a battery holder to house the AA battery, but it really isn't necessary. Simple stick a jumper wire to either terminal of the battery with insulation tape very well, and your battery is ready!

Connect the battery to joule thief as shown in the pictures above. Keep in mind that the LED and the battery share the same ground.

Your joule thief is ready! The LED should start glowing, nice and bright. If it isn't, check all connections again, and check the polarity of the LED.

Here's the video again... It'll help you understand some concepts while being a bit funny at the same time...

Step 5: Conclusion...

Of course, there are several other Joule Thief circuits or there on the Internet. Some use toroidal inductors, some transformers, and some ICs. Here are some other circuits you can try out...

As the circuit is small, you can easily sodler the components to a tiny, compact PCB...

I could run several LEDs in series with an AA battery and this circuit. This means that this circuit can produce much more voltage than that of an AA battery.

You can use a dead AA battery with this Joule Thief too. 'Dead' batteries usually give less than a volt, as shown in my video. However, Joule Thiefs can easily amplify that to easily power an LED.

You can use a high power transistor in place of the BC547, if you want to run high current devices (for eg. 1W LEDs, as shown in the pictures above).

Some blokes have shown how to power high voltage CFLs with an AA battery, using a different kind of Joule Thief. Click here to find out more...

If you are creative and love electronics, you can do just anything with this awesome circuit. The possibilities are endless!

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