Yes, it's the infamous Joule Thief, in Instructable form! For those of you who don't know, the Joule Thief is a tiny little circuit that allows you to drive a white or blue LED from voltages as low as 0.5 volts. You think those batteries are dead? Don't throw them out yet! Hook them up to the Joule Thief to squeeze every last drop of energy out of them!
The idea and circuit came from this Make weekend project. Why don't you pay them a visit?
The idea and circuit came from this Make weekend project. Why don't you pay them a visit?
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Signing UpStep 1: Parts and Tools
For this project you will need very few tools and parts, as you will see in the picture below.
But for those of you who like it in text, here it is:
Helping Hands (Optional)
Soldering Iron
Solder
A Blue or White LED (Other colors are fine, too)
2N3904 Transistor or equivalent
1k Resistor (Brown-Black-Red)
Toroid Bead
Thin wire, two colors (magnet wire works)
You can get the toroid and transistor from a dead CFL; the transistor is usually labeled 13002.
Also, if you use a 2N4401 or BC337 transistor, your LED will be brighter because they can handle more amps.
But for those of you who like it in text, here it is:
Helping Hands (Optional)
Soldering Iron
Solder
A Blue or White LED (Other colors are fine, too)
2N3904 Transistor or equivalent
1k Resistor (Brown-Black-Red)
Toroid Bead
Thin wire, two colors (magnet wire works)
You can get the toroid and transistor from a dead CFL; the transistor is usually labeled 13002.
Also, if you use a 2N4401 or BC337 transistor, your LED will be brighter because they can handle more amps.
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um.. forgive me, i just a beginner
This bike flasher uses a single transistor to flash one or two white LEDs from a single cell. And it uses a fridge magnet for the core of the transformer. This means anyone can build it with common components.
Cut a small fridge magnet into four pieces and make sure each piece sits the same way on the previous piece. The size of the pieces do not matter. 1.5cm x 1.5cm works well. Now wind 30 turns and then another 30 turns. Build the first circuit and connect the wires. If the circuit does not work, swap the feedback wires.
Now add the 10u electrolytic and 100k resistor (remove the 1k5). The circuit will now flash.
http://www.talkingelectronics.com/projects/200TrCcts/images/BikeFlasher-Amazing-1.gif
The circuit they are in has a 3-pin device labelled only "8N 11027" & a 2-pin device w/o any label.
I thought I might rebuild it with a joule thief that would work with 3 white leds off 2 D-cells. Can you help?
Can anyone tell me if I can use this circuit to light 5 leds (3V), but from a 2.4V input?
Thank you!
I have seen lots of comments asking it a transistor type BCxxx 2Nyyy ( you get my drift ) would work.
I would suggest that anyone asking can easily find out quickly by using google search.
It needs to be an NPN transistor and if you search for say hsd965
you will find it is an NPN transistor. check which pin is collector, base and emitter and connect them as explained in this instructable.
The only time you might get a problem is if the gain ( Hfe ) is very low.
The hsd965 is quite high power and it's gain is high too.
If it still doesn't work then assuming you have all the connections made you should try reversing the connections for ONE of the wires. In the picture above for example swap the 2 orange connections over.
Hope this helps.
I can't figure out what is could be different in my setup that requires the cap.
Any thoughts?
Take apart a burned out spiral lightbulb.
I couldn't get it to work though until I removed the resistor.
Works fine without one.
It works with the said resistor if I put it at the beginning of the circuit, but of course the led is dimmer.
Nothing I tried otherwise worked.
What is the reason for the resistor?
I'm sure that Question has been answered before but I don't care enough look through 641 posts to find out.
Anyone want to take a sec to answer this?
I'm using a ferric torrid,
magnet wire,
<1.5v AA Batt.,
2n3904 transistor,
NO resistor???
It is Not supposed to be in series with the led like the usual job of current limiting.
With only 1 battery, going without the resistor (I hear) should work fine.
Does the LED matter? my toroid is about the size of a dime...is that big enough? What size wire is best...is enamel okay to use? Does it have to be a WHITE or BLUE LED? I am also testing with a new AA battery
any help would be great!
And I really can't figure it out, at all. :/
People always tell me they did everything right and it still doesn't work.
Assuming you have checked for shorts, etc, have you tried a different transistor? Maybe you burned it out.
You know the two wires coming out the other side of the toroid? You could try switching them.
After that, I'm not sure what to do. Maybe it's a thing with the toroid? Tell me if it's magnetic or not.