I was on eBay and saw some small green ferrite toroid cores, ten for 99 cents including shipping. I figured that since I had bought some larger green cores a few weeks ago and liked them, I couldn’t go wrong buying these since they were less than ten cents apiece. They were sent from an
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Long ago I built DC-DC converters using a toroid made with tape wound core. The cores were about 2 inches O.D. and we used regular 12 AWG solid insulated house wire for the primary windings. Even so, these cores vibrated a lot at several hundred Hz, making a screeching noise. I saw some very small
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I designed my Blue Blinky with a daylight shutoff, using a LED as the light sensor and an additional transistor to amplify the minuscule current that the LED puts out. This worked just great because there is the point across the timing capacitor where the current is very low, and it takes very little current
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I captured this off a video and tried to make it a bit more readable. I think it was from Sanjev. I built it and it does work at 40 millivolts. The 2SK170 JFETs are not common, and may be difficult to obtain. Other JFETs can be used, but I haven’t tried them. I wrote
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This has been blogged, here and here. I added a CdS photocell (resistor with a circle around it) to shut it off during daylight, thus conserving the AAA cell. I used a 100k resistor for the base bias, so it draws very low current from the cell. I can then call this a low power
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I have often seen schematics of Joule Thief chargers for use in charging Ni-MH rechargeables from used alkaline cells. The idea is to boost the voltage of the used alkaline cell up to high enough to get current the flow into the Ni-MH cell. One setback is that conventional JTs are only 50% efficient, so
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It’s been awhile since I blogged this, so I may be saying what I’ve already said before. But I get comments from others about how to make measurements of the LED brightness. A recent one is in the comments of an older blog. Many Joule Thief builders don’t have the minimum tools needed for some
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I bought some cat# TOR-74 from All Electronics for 4 for $1.00. They say these toroid cores are Magnetics ZF410057C, but Google didn’t turn up any data on them. They are coated Grey, and are 9.5mm O.D., 4.5mm I.D., and 5.0mm high, or .375 inch O.D., .178 inch I.D., and .197 inch high. This is
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I culled through a bunch of AA and AAA cells to find any that were dying or nearly dead. If I found any that were below 1.2 volts they were considered dying, and below 1 volt, they were considered dead. I then put some of the dead ones into Joule Thiefs to suck out the
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I built this special Joule Thief a while ago, and I don’t remember if I wrote a blog about it. I wound the two normal windings on the toroid core, then I wound a third winding of 20 turns for driving the LED. But instead of driving the LED directly from the transistor, I connected
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