The inevitable: I make an instructable on: the Joule Thief.
This is a great circuit to teach children about electronics especially inductors and coiling considerind it contains so few parts and is so easy to make...
Let's get started.
To get us started, I have a video.
By the way: I had forgotten to put the arrows for the LEDs...sorry.
Step 1: Materials, Materials, Materials
1 "dead" battery (with 1 volt left.)
1 2N3904 Transistor
1 handmade inductor or two pre-made.
1 Solderless breadboard
Step 2: The Inductor.
Well, I think you'll stick to the one in the second picture.
The 4th photo and beyond is courtesy of Evil Mad Scientist Labs. When I was making mine, I didn't realize that I had used enameled wire instead of colored CAT cable wire.
Step 3: The Circuitry.
Anyways, I omitted the 1k resistor. I don't know what it does but for now, i just know that I can power more LEDs. It might have something to do with current supply. If you know, please leave a comment.
So, build according to the schematic. Just remember, the two tabs that are tied together are the same tabs that connect to the positive of the "dead" battery.
Step 4: Fin.
One "dead" battery will give you about 65-70 hours of constant use. If you only use it at night then you would have a lot more time.
As always...if you experience any problems leave a comment and I will try my best to help you.
If you did make it successfully well then...leave a comment saying you made it successfully!
Step 5: Troubleshooting.
When I used a multimeter, it showed 1.2 volts going into the white, 3.6v LED. (The battery was 1.3v.)
A scope would show you the pulses though...
Well, there's not much I can explain about this circuit...but I'll do my best if you have any questions.