I have one of those mini LED flashlights. It has a white LED, which has a turn on voltage of 3 something volts, right? Yet the flashlight runs on a single AAA battery, which only supplies 1.5 volts, right?
How is this possible? What kind of black magic is going on inside my flashlight? And, can I exploit it to power several LED's in my circuits without having to use a 9V or 12V battery?
Is there any way to make it smaller? Like is there an IC I could buy? Also, isn't the toroid just acting as an inductor? Could I use an inductor instead?
The Joule Thief has a very small output current so the single LED is lighted but it is not bright.
There are powerful voltage stepup iCs that are made for very bright flashlights.
Yeah, I've been using Maxim-IC step-up converters. But I mean, can I also get 18V or more from a joule thief? If these are capable of x12 multiplication or more, I'd like to know how they do it.
Okay, something about this is jacked up because I tried this with a 10mm white LED and not absolutely nothing. Even the tiny red ones barely got any illumination and I tired two transformers. Will just any toridal transformer work as long as it has 1:1 coupling?
Okay, something about this is jacked up because I tried this with a 10mm white LED and not absolutely nothing. Even the tiny red ones barely got any illumination and I tired two transformers. Will just any toridal transformer work as long as it has 1:1 coupling?
I built a couple of these: 1.5 VOLT WHITE AND UV LED DRIVE CIRCUIT (scroll down to "A Circuit Enhancement") and they worked great. It's just a variation on the Joule Thief idea. I used the 20-tap-20 windings on generic small ferrite toroids using 30 gauge magnet wire as suggested. One fully charged NiMH AA cell ran a 3V white LED for just about 7 days straight before it dropped to about 1/2 brightness.
Torben
Edit: I found a photo of the thing. The tape is just to hold the 30 gauge wire and AA cell in place; the big plastic spike was just over the LED for giggles.
By the way, when people are building this: is anyone using breadboards? Normally I won't solder this kind of thing until I've seen it function on a breadboard first. But the the board's stray capacitance is in the way...well...does this also work on breadboards?
By the way, when people are building this: is anyone using breadboards? Normally I won't solder this kind of thing until I've seen it function on a breadboard first. But the the board's stray capacitance is in the way...well...does this also work on breadboards?
Mine works just fine on the breadboard. The only component I found that was all that important was the transistor, and it was perfectly happy with 4401, 3904, 2222, and so on, so even that wasn't terribly important.
Again, the one I built wasn't exactly the Joule Thief, but as far as I know it's essentially the same idea.
Good call one the modified version. That one is working for me and everything seems to work at max brightness. I used a 2N3904, a 1N4148, and a ceramic 0.1uF capacitor in parallel with different LED variations. My 1watt XLamp was bright enough to provide reading light to a 10x10x10ft room. That's the brightest I've seen it since I bought it over a year ago.
I tried to power a 556 with it, but no luck. I was only getting 3 volts out of the joule thief though, so if you have a better toroid, then you might very well be able to do it.
I saw your site, and I'm trying to learn AVR too! Sh*t is hard! Your stuff is amazing though. I like the PS2 controller project. I'll be happy if I can just get some LED's to flash.