Summary of Maglite Joule thief
This article describes building a Joule thief flashlight using a Maglite body to extend the life of "dead" AA batteries. The circuit acts as a step-up converter, allowing a single AA battery to power the light even when its voltage has dropped below standard operating levels. The project aims to reduce battery consumption while maintaining the option to revert to traditional incandescent bulbs if needed, though the author notes the Joule thief's light output is sufficient for most cases but not as strong as a direct lamp connection.
Parts used in the Maglite Joule Thief Flashlight:
- Maglite body
- Joule thief circuit
- Single AA battery
- Traditional incandescent lamp bulb (optional)
The Joule thief is a really fascinating circuit, simple yet very intricate. Basically, it’s a step-up converted in its most elementary expression. I will spare you the theory since there is plenty of information on it on the web; rustybolt.info is a good place to start.
Joule thieves in all sorts of forms have been featured countless time on DIY websites and I felt it was time I build one. However, I did not want to leave the circuit at the breadboard stage because as it stands, the joule thief has characteristics that make it very attractive for all sorts of low power applications and I figured a flash light would be a very good home for a joule thief, where having the option of using dead batteries is certainly a big plus not to mention using less cells because the circuit steps the voltage up. Why dead batteries? Because a battery is never really dead, its voltage just falls down logarithmically until it hits a point where the device it was powering up stops functioning, which does not mean the battery is totally drained but rather that its voltage has fallen below a usable level. Since joule thieves are step-up converters, they can take that “dead” battery, and give it a new life by stepping up its output voltage to usable levels again.
The build
For my flashlight, I opted for a maglite body for its sturdiness and simplicity. I have been using those for years and they have served me well, but with traditional incandescent lamp bulbs (I do know they make LED versions now), they eat through batteries like crazy. So the challenge was to convert a 2 AA battery maglite so it could run off a joule thief circuit and a single AA but could easily get converted back to using a lamps(As I will tell later, the joule thief’s light output is not so strong … sufficient in most cases but not strong).
For more detail: Maglite Joule thief
- What is a Joule thief circuit?
It is a step-up converter in its most elementary expression. - Why use dead batteries with this project?
A battery is never really dead; its voltage just falls logarithmically until it hits a point where the device stops functioning, but the Joule thief can step up that voltage to usable levels. - Can this flashlight run on fewer cells than usual?
Yes, the circuit steps the voltage up, allowing it to run off a single AA battery instead of two. - What type of Maglite body was used for the build?
A 2 AA battery Maglite body was chosen for its sturdiness and simplicity. - How does the light output compare to a traditional lamp?
The Joule thief's light output is sufficient in most cases but not as strong as a traditional incandescent lamp. - Is it possible to convert the flashlight back to using lamps?
Yes, the design allows it to be easily converted back to using traditional lamps. - Does the Joule thief consume more or less power?
Using a Joule thief helps use less cells and extends battery life by utilizing energy from batteries that are considered drained. - Where can I find more information on Joule thief theory?
Rustybolt.info is suggested as a good place to start learning about the theory.
