white or blue led lights at almost 3 volts.but by using joule thief you can run leds at even 0.5 volts.but in this instructables i will be using 1.5 volt battery.you can use the last bit of energy in the battery using this circuit.i am not good in electronics but even i could do it because it is easy.using this you can reuse dead batteries and help in greening of earth so lets start..its easy and great for scientific classes and experiments.

Step 1: Things You Will Need

this is a cheap project .things needed are also common and cheap.this are the things that you will need:
1)some thin wire.
2)a white or blue led.
3)a 1000 ohm resistor.i got mine from a toy.so leads are small.
4)any npn trnsistor-1.(but transistors like 2n3904 or 2n4401 or bc337 etc are good choice)but if you use pnp transistor you will have to reverse the polarities.
5)a ferro magnetic core like toroids.if you dont have toroids then take the circuit of a decreased fluorecsent bulbs .there you will see one type of round nut wrapped in wire.there you have your toroid.
6)an aa battery

tools you will need:
soldering iron or pliers

beside the things picture you may see white dots.those are reflections of flashlights.

Step 2:

take wires of two colours and of same size.different colours does not matter. it is only for recog nizing the wires correctly.

Step 3: Wrapping the Toroid

take the wires together and start wrapping the toroid.after wrapping you will find four ends.two of blue wire and two of red wire.now twist and connect one end of blue wire to one end of red wire.

Step 4:

first take the transistor and put it so that the flat side is facing up and leads are facing at you.now the lead on left side is emitter and middle lead is base and the lead on right side is collector.now take the led.the lead that is longer is positive and the one that is short is negative.now put thpositve lead of led on collector of transistor led and negative side of led on emitter of transistor .now solder them or twist the ends using pliers.

Step 5:

now take the 1000 ohm resistors and connects one of its end to the base or the middle lead of the transistor.

Step 6:

now from earlier wrapped toroid there was four ends among whom two ends were twisted together.now there were left two free ends.attach one of its free ends to the resistor.and attach the the other end to the collector of the transistor.

Step 7:

now if you want attach a wire to the emmiter of the transistor.now touch this wire to the negative side of the battery.in the toroid were two wires twisted together.touch the twisted end of the wire to the positive end of the battery.then you will see the led glow.

Step 8: Troubleshooting

if your joule thief does not work then check the following things:

1)check whether the wires around the toroid are broken or not.if broken replace it with new one.

2)check whether the poles are right.

3)you may try by not using the resistor .my one worked by not using it.

but even after these if your joule thief does not work then it is bad luck.

i hope you liked these instuctable.feel free to ask any question .i will try to answer according to my ability.

i dont know english much as it is not my mother tongue language.and so if any mistake help me find it.give some more ideas.feel free to ask questions.i will try to answer them as much as possible for me.bye!have a nice day