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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I was reading some of Geo John’s projects and came across a crystal radio set that he built using two tuned coils. A crystal radio set refers to the type of detector used, which was once a galena crystal and a ‘catwhisker’ to find a sensitive spot on the crystal. Nowadays, that is no longer
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A few years ago the Joule Thief fans and others built many projects with a very popular toroid core that was sold from Electronic Goldmine, a surplus electronics company, for the affordable price of five for a dollar. Eventually the supply was all sold and it was no longer available. The stock # was G6683.
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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’ve built an FM microphone bug or transmitter before, but it’s been a very long time since I wound coils for one. Long ago I would wind too many turns on the coil and try it out. The usual outcome was the bug would be transmitting somewhere in the low TV channels 5 or 6,
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I was at Daiso, the dollar and a half store where everything is labeled in Japanese. I saw a little gizmo that looks like it runs off batteries, and heats up a fine wire to melt and seal plastic bags. I got to thinking about it after I left without one. A few years ago
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I bought a few dozen 1 watt LEDs when they were on sale last year at Electronic Goldmine. They go on sale periodically, for well under a dollar each in a package of 5. A while back they offered daylight but recently they have all been warm white. These are surface mount, so they are
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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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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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