Here’s 2 pictures I posted to my watsonseblog in 2009. They’re a picture of a conventional Joule Thief, and one of my Supercharged Joule Thiefs that I built to make sure that the first one or two were not just accidentally ‘too good to be true’. The Supercharged Joule Thiefs worked so well that at first I thought it was just a fluke. But they all performed much, much better than the conventional JT. You can see the schematic and data here.
SJT Circuit Description
The circuit is not complicated, almost as simple as the conventional JT. The resistor is a 3.3k, but most of my SJTs use a 1.5k resistor, which gives about the same amount of light as a conventional JT. This resistor depends on the gain of the transistor and how much light you want from the LED.
The transistor is a BC337-25, which has its printed face towards you. For the PN2222A, 2N4401, etc., the face would be away from you. The diode is an old germanium type, which works okay. Just about any diode will work: 1N4148, 1N914, 1N5817 Schottky diode, or even the base to collector junction of a transistor. The cathode or banded end is on the right.
The capacitor shown is a “561” or 560 picofarad ceramic disk capacitor. A 680, 820, or 1000 pF capacitor will also work, with 680 probably the best choice. Any type should work, plastic, ceramic or whatever.
Conventional JT
I may have posted these pics earlier. I hope not. So many blogs, not enough time to index them in a list. I did that with my watsonseblog, then it was removed and all that work was gone and wasted.