Build a simple Joule Thief

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A Joule Thief is an awesome piece of circuit that will suck out all the remaining juice from your leftover and old AA batteries to do something worthwhile, in our case, light LEDs 🙂 . No, really! It does exactly that and you will find out once you build it yourself. So what are we waiting for? Lets get started!

What you need

Following are the things you will need.

  1. 2N222 transistor – 1pc
  2. 1kΩ resistor – 1pc
  3. A ferrite core – Now this is a bit difficult to get. You can get it from old CFL lamps which have one, its the one that looks like a black ring. OR You can also use a small centre tapped 9v transformer. I will be using the ferrite ring.
  4. 2 Thin wires – say a meter long each.
  5. An LED

Here is a pic of the parts

What to do

Lets get to the circuit. The following is a circuit diagram.

  1. First mark the end of the wires with colour so that you can easily identify them. If you have coloured wires already, it’s all the same.
  2. First take the wires and place two of them side by side. Holding both of them together, wind it around the ring carefully.
  3. Then, join the two alternately adjacent wires together (note this step, if you don’t get it see the circuit diagram)
  4. Connect another end of one wire to the resistor connected to the base and the other wire to the collector.
  5. Add in the LED.
  6. If you are using the centre tapped transformer, the centre tap goes to the positive and the other connections are same.

Now get an old AA battery (of course a new one will also work) and connect it. Viola! The LED glows on less than 1.2v input! You can experiment with all sorts of old and different batteries and finish them for good. Finally a use for those old batteries 🙂 . This is how it looks when all of it is cleanly soldered.

Had fun? Check out the following projects too.

Feel free to ask any queries in the comment section below.