Durable Laptop Batteries
How a Joule Thief Works
Step-by-step run through of how a Joule Thief circuit works. Includes how all the parts, the 1.5 volt AA battery, the resistor, the transistor and the ferrite core with its two coils of wire work together to build up energy in a magnetic field which then collapses to produce enough voltage and current to light an LED (Light Emitting Diode.) This includes explanations of the feedback that rapidly opens the transistor between base and emitter to open up the emitter to collector too. And also the feedback that slams the transistor shut again. See also this video on How to Make a Joule Thief (called Make a Joule Thief for Zombie Batteries): youtu.be And also this webpage about Joule Thiefs: rimstar.org Follow me on Twitter: twitter.com rimstar.org
Video Rating: 4 / 5
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I have? never run it until it stopped.
How long will? the battery last
actually, I do not believe this is faked… I have boost converter? circuits similar to this that work very well…
Thanks.?
very? nice
Believe it or not,? the frequency is actually very much controllable. Here is a joule thief circuit built in a simulator. Try changing the values of R and the L of the transformer to adjust the? frequency. Smaller L increases the frequency.
tiny(dot)cc/ouxvsw
The default frequency for that circuit is ~ 200Hz
Wouldn’t work. During one part of the cycle the current is in? a direction to turn on the transistor, but during the second part of the cycle the current reverses due to the direction of the collapsing magnetic field and quickly shuts off the transistor.
Replace the resistor with a? diode^^
so.. If I want this process to go WAY slower so the human eye can se the flashings,? do I just change the resistor?
The resistor size does matter. Some people even put a variable resistor/potentiometer and find a resistance that results in the LED being brightest that way. For the circuit in my “Make a Joule Thief for Zombie Batteries” video I used a 1 kilohm resistor.? You want something that doesn’t limit the current too much while still protecting the transistor, which is why it’s there. Some have gotten away with no resistor at all.
does it matter what size? resistor?
I think you need special microwave gallium arsenide transistor for that frequency anyways.?
It’s not cycling based on a resonant frequency. In the video I talk about the cycle? reversing because the core becomes saturated. But I mention that as one of a few possible reasons depending on things like the battery voltage. At these low voltages, most likely the cycle reverses when the current between base and emitter is too low for the increasing current between the collector and emitter. So the timing is due to the transistor specifications rather than a resonant frequency.
So… The circuit has a resonant frequency?then does that mean I? can design it so that the frequency is 2.4GHz and attach to a simple antenna? (Transistor gated with an alternate load so that the circuit would still go through the cycle) a simple mobile jammer?
Yeah, it was pointed out before. I was? thinking more in terms of diodes when I made that explanation.
Excellent!? Thanks for letting me know!
Just? made one which works very well.
Used a Tip 122 NPN Transistor.
You can hear a slight hum in operation.
Was great building it with your explanation as a guide.
“…this path between the collector and the Emitter is closed unless there is enough _voltage_ across the base and emitter…”
Correct but not the best representation of what’s going on. The Bi-polar Transistor is a current amplifier, so more correctly: “…this path between the collector and the? Emitter is closed unless there is enough _current_ flowing into the base and emitter junction…” It’s the current flowing in the base of the transistor that controls the collector current
I randomly chose the number of turns shown in the diagram when I made mine. For transistors, some suggestions are 2N4401, NTE123AP, BC547B, 2SC2500, BC336, PN2222. See my video on how to make a joule thief called “Make a Joule Thief for Zombie Batteries” where I go over all this. You can find a link to it in the description? below this video and on my channel page.
how much turns around? the feriode, can you also suggest a transistor please