Joule Thief: Basic Circuit, Upgrade to 24 LEDs, 1 to 1 Toroid Winding
The basic circuit using the 2n2222 metal can transistor, with a few alterations from the “instruction” video, to show the next steps in development. I’ve tested a few different coils and this 1::1 toroid with bifilar 14 turns of #22 solid wire works just fine for this stage of the game. You can also use the same 10::30 or 10::50 coil used in the Basic Instruction video; compare, contrast, record, report. I put in a 10K trimpot instead of the 220R base resistor, to show what happens when you vary this resistance. I constructed a LED bank by making two rows of 11 green LEDs in series, then putting the two rows in parallel. This bank is connected to the usual Emitter and Collector of the transistor by two more LEDs. The polarity of all these LEDs is the same as in the Basic video: anode towards Collector, cathode towards Emitter. (NOTE: actually the arrangement on the breadboard could more accurately be described as 11 sets of two parallel green LEDs, with all the sets in series. The result is the same, electrically, I believe– although I’m going to have to try it out to be sure.) Varying the base resistance not only varies the current thru the system (mostly by varying the base-emitter current I think) but also varies the frequency of the oscillations. I’ll scope this system in the next video to see better just what is going on with the voltage and base resistance changes.