I was watching JonnyDavro’s Joule Thief driving a power transformer, which is used in reverse to step up the voltage to drive a CFL tube. He shows the schematic, and later says that the unlabeled transistor is a BD139. I added a comment, saying “What amazes me is that you’re getting these high voltages at
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The first thing that comes to mind when the experimenter wants to find out how much current is flowing through the LED is to measure it with a DMM set to read milliamps. This works okay if the LED is connected in series with a current limiting resistor. The DMM will add maybe 10 ohms
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Most silicon transistors have an emitter to base reverse voltage rated at 5 volts maximum, with some transistors rated as high as 6 volts. Old germanium transistors were higher than this, but when the manufacturers began to make silicon transistors, they apparently gave up having a higher emitter to base reverse breakdown voltage so they
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I received a message asking several questions about the Joule Thief. The asker asked to be explained in layman’s terms, so I’ll try to keep it understandable. First off, I do not use a Spice program to simulate the circuit. I used LTSpice a few years ago, but not any more. Why should I when
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I often read where people add the rectifier and filter capacitor between the coil/transistor and the LED. They claim that it increases the efficiency. I just want to clarify what I see is happening as the Joule Thief is operating. My observations are based on what I see on an oscilloscope connected to the JT,
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Joule Thief Special There are thousands of different types of transistors, made by hundreds of manufacturers. But it takes a special kind of transistor to give good performance in a Joule Thief. The transistor should have high current gain at high currents and very low collector voltages. A maximum collector current of 500 milliamps
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Happy New Year! My watsonseblog dated 2009 Jan 1 Joule Thief, FET Only is the topic. In April 2005 I built a Joule Thief (circuit is in my blog and at the bottom of this webpage) that used both a 2N3904 BJT and a 2N7000 MOSFET, with the 2N3904 starting the circuit and the 2N7000
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My watsonseblog dated 2009 Feb 19 These may be dupes or unfinished. 2009-02-19 Joule Thief, High Efficiency, #01 Supercharged See the schematic and original blog here. I have built several of these high efficiency ‘supercharged’ Joule Thiefs (SJTs) to try to optimize the parts values, especially the coil. I’m posting these SJT blogs to allow
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My watsonseblog dated 2011 Apr 12 2012 Apr 12 JT Toroid Turns, Inductance I have some answers to the questions I read here. What are the inductance ranges that work in the Joule Thief? What are the limits to the choice of turns? What is the maximum number of turns and the minimum number
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On Youtube, this guy named Xee2 or Xee2vids posts short videos of schematics, projects and circuits. There is no motion, just slides, and no narration, no voice in his videos. There is no way to comment to tell him if I’ve found a mistake. But so far, most of his vids are very good with
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