A Joule Thief circuit is a simple three component, low Voltage DC-DC boost converter. The circuit can run on voltages as low as 300-400mV depending on the transistor used and windings on the transformer. The output voltage and current depends on the three components used in the circuit. As a minimum the transistor must have high enough gain and should have a Collect-Emitter Voltage rating that is well above the maximum output peak voltage on the secondary winding ( I like at least a 25% margin ). The resistor is chosen so that it limits the maximum circuit current, by limiting the current to the base of the NPN transistor. The transformer can be wound 1:1 for simple operation or can be wound with more than two coils ( A third winding may be wound to create high voltages for running EL devices, nixie tubes, neon bulbs, etc... )
I decided to try and experiment with this circuit myself. I have made many variations of the circuit, some that could run to voltages as low as ~350mV and still produce 12V out (not much current though with such a low input voltage). In making the circuit, I decided it would be nice to have a PCB so that I did not have worry about problems that I was having with the air wired experimental circuits. The air wired circuit had several problems due to wiring shorts or opens, and was not robust enough to carry around. I thought it would be nice to produce some kits for other experimenters so that it would be easy to assemble and not have to worry about wiring problems. Visit the products page or see Joule Thief kits here: http://www.madscientisthut.com/Shopping ... ief%20Kits
So I have created my very first PCB and sent out for fabrication on Oct 17th. The PCB's finally arrived today (Oct 27th). I built the first Joule Thief kit using a 2N2222 T0-39 can package as I am waiting for the T0-92 plastic package 2N4401 to arrive tomorrow. I tested this one on the bench it starts up at 520mV and shuts down at around 470mV. At 1.55V in the circuit was drawing 100mA. I cannot wait to get the 2N4401 and build another one to see where it is running at.
For the JT_001b_ASM user manual click here: http://www.madscientisthut.com/pdf/JT_0 ... manual.pdf
For JT_Kit001b assembly instructions click here: http://www.madscientisthut.com/pdf/JT_K ... ctions.pdf
To read about the homemade Zinc Copper Battery Experiment click here: http://madscientisthut.com/wordpress/?p=46
