Led With a Single AA Battery Aka Joule Thief




About: im a tech lover. I build Electronic Projects time to time. Please follow me for upcoming Instructables.

In this instructable you will able to make a simple led hack which can power a led with single a AA 1.5v battery. A LED need at least 2.4 v or more voltage. This circuit will boost the voltage up to drive a single led. But it will consume more current than a led need due to conversion of the voltage.

Step 1: The Parts You'll Need to Build This Project.

You'll need
1.a LED (I have used a bright white led)
2. A NPN transistor any low power will suffice I used BC 548B because it's easily available and I use this transistor all the time
3. A 1kilo ohms resistor.
4. A toroidal core (I salvaged it from a old CFL.
5. Some thin single strand Copper wires (salvaged from cat5 cable.)
6. AA battery.
7. Breadboard. Or perfboard (if you want to make it permanent).
8. Soldering iron ( again if you want to use the perfboard then you'll need this).

Step 2:

Making the toroidal coil.
This is the main thing that you have to make yourself. It's fairly easy to do. Pick two single strand wires from cat5 cable. Or you can use any thin wires. But make sure you use to different colored wire. Hold the two wires and wind in the toroidal core. 8-10 turn will do the job. And look carefully the wires don't overlap. Then cut the excess wires.

Step 3: Put Everything on the Breadboard According to the Schematic

First place the transistor on the breadboard the transistor pin mentioned on the schematic. Then connect the led. Then the coil and the resistor. If you connect the coil wrong way it may not work. Check the schematic. power the circuit with a AA battery if everything's okay Led will glow. Thanks.



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    8 Discussions


    2 years ago

    Nice joule thief design.


    2 years ago

    a nice piece of work you've shown...but what about the toroidal core...should i use any type of cicular core..or that core needs to be made of some specific metal???

    2 replies

    Reply 2 years ago

    I've used a ferrite core from a damaged CFL lamp you can use any core but it must be magnetic material


    2 years ago

    Interesting. Was this based on some circuit you ran across? This circuit must be a self-resonant oscillator with the LED rectifying the AC and adding it to the AA's output. I'm curious as to what the oscillation's frequency is? Have you ever tried an LM3909 LED blinker IC (from the late 70's)?

    1 reply

    Reply 2 years ago

    The Joule thief concept of a minimalist step up voltage converter dates back more than 15yrs ago, it was very popular back then. This design is well known, and there's dozens of variations on the Joule Thief.