I have often seen the conventional Joule Thief circuit used in situations where it is a poor choice – there could be better choices that would do the job. The Joule Thief or blocking oscillator circuit transfers a low voltage, high current input to a higher voltage, lower current output, with a low efficiency and
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This is one of those Joule Thiefs that uses an old germanium 2N404. But I got them from a German seller on eBay, and I have a suspicion that they were made within the last decade or so, probably by one of the makers in the former soviet bloc countries. I’ve measured true 2N404s and
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An earlier blog about very lowpower Joule Thiefs is here. I experimented with a very low power Joule Thief using a SS9014 high gain, low noise NPN transistor, a red high brightness LED, a T231212T toroid with two 12 inch (300mm) lengths of 30 AWG (.25mm) solid enameled wire, and a 1k resistor in series
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I had a Joule Thief already assembled, using point-to-point wiring. The transistor was a BC338. The coil was a 3/8″ (9mm) toroid core with a primary winding of about 20 turns of 26 AWG and 666 uH, and a feedback winding of 190 uH. The resistor was 1000 ohms. Modifications I disconnected the feedback (base)
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I have built a few dozen of my Supercharged Joule Thief Flashers using the PC boards that I designed and had made with ExpressPCB (schematic is in the link above and PCB picture is below). The circuit works okay with a fresh battery but when the battery gets low the light comes on solid, and
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In early May I built a Superregenerative FM receiver, and blogged that I should build a 1.5V to 9V DC-DC converter for it. After testing the second DC-DC converter for the DMM, I think that I can use the same Night Joule Thief board for this receiver. A few of the component values can be
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This is the second one I’ve built. The first one I built is in my earlier blog – links to the schematic can be found there. I used the following parts: a 2N3906 for Q1, and PN2222A for both Q2 and Q3. R1 was 470 ohms, R2 was 10k and R3 was 8.2k. Both the
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I’ve blogged this project more than once in the past, (and here too), but I didn’t follow through with the circuit completed and installed in a DMM. Well, I finally got my act together and on the road, and finished the first working 1.5V to 9V DMM power supply. I thought about it and concluded
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Paul got me thinking about the Joule Thief with low battery current. In his nineteenth JT he used the very high performance Fairchild KSD5041, same as the 2SD5041 (Japanese pinout – the center pin is the collector). He thought it was his brightest, and that could very well be. His theory is that the coil
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This Joule Thief uses three SS8050 high current transistors, each having a 333 ohm bias resistor (actually three 1k resistors in parallel). At less than a half volt, it gobbles battery current, 49 mA at 0.42 volts. That is a lot more than the typical JT, which drops to a very low current as the
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