Summary of The simple joule thief using AVR microcontrollers
The Joule Thief is a simple circuit that revives depleted batteries, even those unable to power basic LEDs. It amplifies voltage to extend battery life, powering blue/white LEDs for ~8 days or red LEDs for 10–12 days. The design also supports microcontrollers like AVR or PIC MCUs and was submitted to LED and laser contests.
Parts used in the Joule Thief:
- 470uH inductor
- 2.2K resistor
- Two 1K resistors
- Two basic NPN transistors (2N3904, 2N2222, 2N4401, etc.)
- 1000pf ceramic capacitor
- AA battery and holder
- LEDs
The Joule Thief is such an easy and simple device, but what it does is amazing. It can use a battery that is not usable in any other electronic device and give it life again. It can even take a battery that won’t even power a basic LED by itself when it is brand new (1.5 volt AA) and amplify the power so that it can.
This “Joule Thief” circuit, using a battery that won’t work in any other device, can power a blue or white LED for approximately 8 days straight before it stops working. It could probably power a red LED for at least 10-12 days. You could also use it to power a microcontroller (such as an AVR or PIC MCU).
This is an entry in the LED Contest with Elemental LED and the Hurricane Lasers contest, so if you like it, vote!
Step: 1 Why is it called a Joule Thief?
The reason the Joule Thief is called what it is is because of what it does. (That sentence was confusing) (:
Basically, what the Joule Thief does is it “steals” every last Joule of energy from your batteries. The explanation of what a joule is can be found on the Wikipedia page here. The quickest explanation I can think of is that a Joule is a form of energy that, in the way we use it, can be used to power electrical devices. I won’t go into any more detail here because it gets very complicated.
Step: 2 Parts list
To make this “Joule Thief”, you will need:
1x 470uH inductor (looks like a fat resistor)
1x 2.2K resistor
2x 1K resistor
2x basic NPN transistor (2N3904, 2N2222, 2N4401, etc.)
1x 1000pf (same thing as 1nf or 0.001uf) ceramic capacitor
1x AA battery + holder (or any other 1.5 volt battery)
As many LEDs as your heart desires.
Step: 3 Make it on a breadboard!
It is super simple to make on a breadboard because it has such a low parts count. Look at the schematic to figure it out.
For more detail: The simple joule thief using AVR microcontrollers
- What does a Joule Thief do?
It steals every last Joule of energy from batteries to power devices. - How long can it power a blue or white LED?
Approximately 8 days straight before stopping. - Can it power a red LED longer than a blue one?
Yes, it could power a red LED for at least 10-12 days. - Does it work with batteries that cannot power basic LEDs?
Yes, it amplifies power so even brand new 1.5V AA batteries that fail alone can light an LED. - What types of transistors are used in the project?
Basic NPN transistors such as 2N3904, 2N2222, or 2N4401. - Can a microcontroller be powered by this circuit?
Yes, you can use it to power a microcontroller like an AVR or PIC MCU. - Is it easy to build on a breadboard?
Yes, it is super simple due to its low parts count. - What is the function of the 1000pf component?
It is a ceramic capacitor used in the circuit.
