Joule Thief

A joule thief is essentially a way to "squeeze" as much power out of a "dead" battery. Meaning that batteries that were outputting low voltages could be used in light load applications. In theory, the system is a oscillating voltage booster. Using the transistor to switch the LED on and off at a high frequency, that the human eye cannot detect the on and off switching.

In this project, I was in a electronics class learning about components on a circuit board, transformers, toroids, and at the time transistors. I had found an old circuit board laying around the lab from an older computer. 

Parts

I started desoldering some of the components that were familiar: a toroid, a 2N3904 transistor, resistors, and an LED. 

I also found strips of solid wire at 2 foot lengths. 

Soldering material was available at our lab.

A power supply was also available.

Planning

Although I had this mapped out in my mind, I made a diagram of the circuit to make sure that if I had any other distractions I could come back to work on the joule thief later on.


Using the diagram also help to separate the emitter, base and collector terminals of the transistor. 
I also made the decision to use wire that were two separate colors so that I could identify them for termination, and I was also curious to see if there would be a difference in voltage with increased insulation.

Fabrication

The first thing that I fabricated was the transformer coil (toroid). I wound the wire through the toroid as many times as I could (six times). Soldering the terminals to the respective ends. Making sure to keep correct polarity on the transistor and LED. 

Testing

After fabrication I tested with a known depleted battery, and with a known good battery. Both resulted in great results!




After the initial test I used a digital power supply and also connected an oscilloscope to demonstrate the process of oscillating voltage climbing and being emitted.



Possible Integration

As I was building this, I was thinking that it would be cool to see a whole line of flashlights using this technology. But this demonstration was cool to show the ingenuity of engineering with spare parts, physics, and a dead battery.

Comments

  1. SandalsFebruary 10, 2022 at 12:52 PM

    Awesome, I just use to put the 9 volt battery on my tongue to see if it had anymore juice in it. Haha

    ReplyDelete

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