I put this together during the Xmas holidays back in 2008. It may have been posted to my watsonseblog, I don’t remember. But here it is for the world to see again. It’s the typical 2 transistor voltage boost circuit – often mistakenly called a Joule Thief – with a BC337-25 for the driver transistor.
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I did learn something from the Grease Spot Photometer Experiment. I found that the grease spot really does work. I can compare the brightness of two LEDs to find out the current in each LED. But then I realized that I don’t really need two LEDs (I didn’t use two with my luxmeter measurements). All
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I had some short lengths of wire laying around, a 1k resistor, a red LED already soldered to a transistor, and this half of a broken toroid. After a few minutes of fiddling, the result was this working Joule Thief. It shows you can make a JT that works from just about anything even if
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I got some SMT power inductors from dipmicro.com because I read that they were only 0.18 ohm and could handle almost 2 amps. The winding is on a ferrite bobbin and that is covered by a ferrite sleeve to give it a better magnetic path. But there is still an air gap between the bobbin
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I’ve been interested in very low voltage converters for quite a while. I blogged this document several years ago in my late great watsonseblog. Almost a month ago I was commenting on a circuit, often called a Joule Thief, that was powered at 27 millivolts by a Peltier junction and the heat from a guy’s
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I was watching a Youtube video of Xee2vid’s no toroid Joule Thief 4, which is a conventional JT that uses a Radio Shack 273-1380 audio output transformer (Xee2 doesn’t allow comments). The ad doesn’t say what the specs are but IIRC, it’s a 1000 ohm center tapped primary and an 8 ohm secondary. The small
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The typical JT coil is wound bifilar, two windings at the same time. Winding the wire at the same time makes it easier, and it’s electrically the same as if two separate windings were wound. I often use 24 AWG wire and wind the coil bifilar. But I also wind it using four pieces of
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I have built a number of the two transistor “Joule Thief type” V boost circuits, and they work okay. I am comparing the two typical types: the PNP – NPN and the NPN – NPN types. The common one is the PNP – NPN type which uses a PNP transistor for the first transistor and
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I built this up – tack soldered it together – before I drew the schematic. My intention was to make a circuit that was very low on power when the light deactivated it, and to use parts that the neophyte experimenter would already have. I wasn’t concerned about complexity or cost, but the three extra
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Using a resistor in series with the LED or supply The reason for using the 1 ohm current sensing resistor between the LED cathode and negative is that it has lower resistance than the meter. The meter’s internal resistance varies depending on the range setting so one can’t depend on getting consistent readings between ranges.
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