I was digging in my basement and found a flash light, no ordinary one though, it is a hand crank flashlight, that turns a disk which alternates positive, negative, positive, negative, etc, to change the magnetic field, which displaces the electrons creating AC power for the bulb. sorry if I explained that wrong, I'm sure Kerm, an Elec. Engineer will swoop in to clear that up a bit, as I'm only a mere HS student lol. anyways, would it be possible to maybe splice a few wires (so to speak), with the flashlights hand-crank power generator, with a charger for a mobile device, to in return "charge" the device?

Is this possible? or am I just dreaming here. Should i still try it?
any suggestions or comments? thanks

Are you sure it's AC and not DC?
It has to be DC for it to act as a charger if that's your idea. I'm not sure whether it would generate the necessary voltage, though.

I'm pretty sure it creates AC power, because of the shifting electrons, but like I said, I could be wrong

Normally, flashlights don't use AC power.

The reason why I think it's AC is because if you crank it say, for two seconds, the light stays on for about two seconds, then takes about a second to die out, since the disk with the magnets on it is still spinning for about a second after the cranking stops.

That doesn't mean it's AC
And what do you mean, shifting electrons? You can't see them moving, can you? DC moves electrons too. Do you mean it as a synonym for AC?

The hand-cranked torches I've used have all been AC, as it's simpler to build an AC generator than a DC one and incandescent bulbs work with either.

This page on power supplies has some useful information on rectification (converting AC to DC) and regulation (keeping the output voltage at a fixed, safe level).

very interesting, thanks

A hand-crank generator works by the properties of Electromagnetic Induction. In a nutshell you turn the crank, create a magnetic field proportional to how fast you're turning the crank, this magnetic field then induces a change in potential (voltage) in the core of the generator (i.e. a wire), and when you have a closed circuit involving the core, current will flow and you can power whatever load that you have attached.

Also, I doubt it's a DC generator because AC generators are much cheaper and simpler to produce.

is it still possible to charge something using AC tho?

You have to convert it to DC first. Batteries are always by their very nature DC devices.

I was looking around on the internet, and I guess I have to use a 4 diode bridge rectifier to convert from ac to dc.. but there are different kind of diodes that supply different amount of amps... what I don't know is... how many volts go into a device when it is being charged?

It depends on the device you want to charge.

Quite a few devices will charge at 5V these days (a fairly standard voltage; USB ports run at 5V, for example). I don't think that the device being charged will draw more than a few hundred milliamps, so I would have thought that the common 1N4001 diodes (rated at 1A, usually) would do the trick. Check the original charger to see what that's rated.

Do you know what voltage the generator produces when spun at a decent rate? Each diode will incur a 0.7V drop or thereabouts (and as current flows through two diodes in a bridge rectifier that means a drop of 1.4V) and a linear voltage regulator needs its input voltage to be a bit higher than the output voltage (this is called the drop-out voltage, and with the popular LM7805 you should probably account for a 2V drop-out) - to get 5V out you should probably ensure you're getting at least 9V from the generator.

You rock dude seriously
I'm going to take some time tomorrow and buy a few diodes, some wire, and a smoothing capacitor, solder this shniz up, and see if i can get this working For more info on the voltage output of the generator, I shall bring it into my electric engineering course tomorrow at school, and check it on the multimeter, I'll update you guys tomorrow,

I would strongly recommend you check that everything is working nicely (i.e. you're getting a relatively constant supply voltage out of the supply that's not above the rated voltage of the device you intend to charge) before plugging it into the device - getting the power supply wrong can blow up less hardy (and expensive!) electronic gizmos.

This is where a fused multimeter would be invaluable.

I'm having trouble deciding what kind of smoothing capacitor I would need... any help?

As already stated, definitely an AC generator, and use a bridge rectifier and smoothing circuitry to get out clean DC. Borrowing from Wikipedia, here's a simple RC smoothing circuit. Of course, you'd still have to crank at a very constant rate to get constant voltage. Better would be to use the crank to charge a battery or large capacitor, then charge the device from that, imho.

could you use the hand crank to power an AC wall wart which can then charge the device of your choice?

I doubt the generator can provide anywhere near 120V. Though some of the circuitry from one of those may be useful.