How does this dynamo work????

[Batdragon]

I have a question to you knowledgeable people out there.

Background: I had a broken LED torch laying about and i knew I could not fix it so have salvaged the parts from it. The torch worked from a group of button cells, or a hand powered dynamo. I know the basic principals of alternators and dynamos, but this one had me scratching my head.

Here are some pictures of it









The system works by spinning the magnet over the coil. As it is a round magnet with a hole in the middle, and does not pass through the coil, I am at a loss how this can generate power, because the conductor in the coil does not cut through the field of the magnet.

Is someone able to show me how this works and the principals of it, like the flux fields of a toroidal magnet, so I can understand better what is going on

Many thanks for your help on this as it is driving me crazy and I have so many ideas on things I could use this for.

BD

[hiker]

its like a field coil on a car alt...hit it with a few volts--and each one of those little claws will have
n-s-n-s  and so on--the mag must be multie pole....
built a backwards car alt few years back...i used the field coil for power output--i  put a ring of mags
around the  fieldcoil  [did away with the stator]  lite up a cfl 110 v ac  real easy..
  http://www.youtube.com/watch?v=g_J4MI7cU68

[joestue]

I am at a loss how this can generate power, because the conductor in the coil does not cut through the field of the magnet.

that is true, the flux lines do not pass through the coil's conductors (for the most part) but they do pass through the coil.

it is not required that the flux lines flow through the conductor, only around it, and change with time.

[dinges]

It's a claw pole alternator, just like car alternators and bicycle dynamos (both bottle dynamos and hub dynamos).

The magnet isn't as straightforward as it may appear at first sight; it has 8 poles (alternating N-S-N-S...). When it rotates the alternating flux is seen by the 8 claws and guided to the center of the coil, where it results in an induced voltage in the coil.

If you use another small magnet and move it over the magnet of the claw pole alternator, you should be able to discern the 8 zones that alternately repell and attract your test magnet.

Hope that clears it up.  Googling for 'claw pole alternator' will return in more and more detailed information.

[Batdragon]

Thank you that does make it clear to me now 

I have been looking up stepper motors last night and as soon as you said that it all fitted into place.

I am off to the how to store it area now to look up capacitors and batteries so I can get the most out of a hand cranked system.

Thank you all for your help with this, I just needed that picture in my mind.