I bought some ‘high current’ chokes from Jameco, P/N 642855, which are 390 uH. They’re bigger than average, and mount axially; in other words the leads are at opposite ends of the cylindrical package. They are made by winding relatively heavy copper wire onto a ferrite bobbin. The bobbin is then covered by a piece
(Read More…)
I built this up to see how well the blue LEDs I got recently would work on the DC output of a JT. I put three pairs of two in series on a perf board and soldered them to the air wired JT. I knew that the Vf of two blue LEDs was going to
(Read More…)
I was reading this web page about the history of mystery clocks and I got some ideas. One of them I got from my experience with a very old automated voltmeter. I don’t remember much about this voltmeter other than it used many relays and made a lot of noise and the display consisted of
(Read More…)
I went on a Joule Thief building binge for a few hours last night, making up some germanium Joule Thiefs after I found a small box of old unidentified germanium transistors that I had forgotten about. I used a small piece of the “Woodsies Squares” thin birch plywood about 1/2″ by 1″ (12.5 by 25
(Read More…)
I took this picture by holding a two lens pocket magnifier in front of my point-n-shoot camera. I came out good considering that the magnifying lenses had no color correction. That’s why there’s a slight color fringe at some dark and light points. This is an old germanium transistor from the late ’50s or early
(Read More…)
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.
(Read More…)
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
(Read More…)
I thought about doing this since I wrote a blog on it back in the mid 2000s. Use the Grease Spot Photometer Method to compare the outputs of LEDs. This experiment is used in Physics classes to demonstrate the relationship between candles and the distance to the light source. In my case I decided that
(Read More…)
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
(Read More…)
I’m trying to figure out how these Miracle LED people get away with advertising a two watt LED light is equal to a 60 watt light. These are supposed to screw into the sockets of a ceiling fan, and come in a set of four for fifty bucks when tax is included. Also, they say
(Read More…)
