Bloch Wall Generator

[DreamThinkBuild]

Jkgulick, thanks for bringing this information forward. This is neat it's such a simple idea I had to try it.

I whipped up a very simple test. I have an old shaded pole fan motor and a small diametrically magnetized magnet taped to the end of the shaft. Then I wrapped a long cow magnet with about 40 windings of standard 24 gauge wire( this was non-magnetic wire just solid copper). Not the best winding but just something to see if I could get anything out of it.

Now since this is a very un-scientific preliminary test I layed the cow magnet with coil on the table with the spinning shaft over it. As I moved the coil around toward the middle sweet spot I got 1.4u Amps and 1.4millivolts(no load), really small but what is interesting is that the amps and voltage almost mirrored (uamps to mvolts) each other at the sweet spot(bloch wall?, middle?, neutral plane?). As you move towards the ends it will lose voltage and current also you will get a pull on the rotor which will push the motor to the side. The middle area doesn't have that pull.

I can see with a better setup, stronger diametric magnet, a fast rpm low power motor, better and more windings this could really start to generate.

I will do more testing tear it all down and get a better setup going.

I would like anyone else to try to see if you can validate my results. It's really simple to try, these are the parts I'm using.

The fan motor was from a small kids fan that had a cracked blade.

Here is the diametric magnet I'm using. It's pretty small only .754 grams so a high speed motor would have no effort spinning it.
http://www.kjmagnetics.com/proddetail.asp?prod=D42DIA

The cow magnet is this:
http://www.magnetsource.com/Solutions_Pages/cowmagsAlnicoPill.html
Just in case the cow swallows the tractor or something. I picked this up at the local grain store.

[jkgulick]

Dreamthinkbuild, thanks for trying this out.  There's something about it's simplicity and symmetry that makes me think that this is really significant.  If you measured a little bit with your meter, I would wager that at the instant your little magnet was passing near the coil, the current/volatage was much higher, don't you think?  You probably can't notice any drag with what you have now, but that is what is really interesting.  :-)  With big magnets and big coils and high speed, this should really be neat.  Also, I think that the fellow said that his output was AC, but I might be wrong.  Does that make sense? 

[Staffman]

Just some thoughts here.

When the magnetic field changes in the cow pill coil setup due to the rotating diametric disc magnet, would the usage of the induced current in the coil cause push back against the rotating disc? Or would it try to push against only the cow pill's field?

Seems very interesting. I would like to try this out with a larger setup than was discussed above if the push back can be theorized or proven to be null.

[DreamThinkBuild]

@Jkgulick,
It produces AC. I'm also wondering if your first image you have would be a better setup than a long magnet. Use 2 coil wrapped ferrite bars with a magnet in the middle. Have to play with different configurations and see what generates the best. Higher speed does make a big difference though.

@Staffman,

When the magnetic field changes in the cow pill coil setup due to the rotating diametric disc magnet, would the usage of the induced current in the coil cause push back against the rotating disc? Or would it try to push against only the cow pill's field?

That is a good question. I get very little resistance from the small magnet as long as I keep it parallel to the cow magnet and don't get near the ends. I haven't tried putting any load on my current setup, the voltage and current is so minute.

I'm waiting for better parts to come in right now. I finally got some more time to work with it. I did 82 turns of standard 24 gauge wire. My first test was contaminated I noticed that when I checked the frequency and sure enough 60hz appeared which meant the shaded pole fan motor transformer was leaching into it.

To eliminate that I'm now using a battery powered Dremel tool with 2 speeds 10k RPM and 20k RPM. I noticed something odd which is the more turns I put on it the sweet spot seems to move towards the ends(about .5 inch from top of pill) and not the middle.

I got the scope hooked to it now so I can see what this beast is generating. It is quite interesting. This is taken towards the sweet spot or almost near the end of the cow magnet. Using the same diametric magnet as before.

10k RPM

Code Select Expand


CH1 20.0mV  5.000ms 10.00kSa  [Date:2/12/2009]

Vpp 22.4mV
Vmax 12.0mV
Vmin -12.8mV
Vavg 1.99mV
Vamp 18.2mV
Vtop 7.67mV
Vbase -5.54mV
Vrms 5.82mV
Vover 32.4%
Vpre 10.4%
Frequency 149.0Hz
Rise Time 2.000ms
Fall Time 2.100ms
Period 7.100ms
Pulse Width+ 3.300ms
Pulse Width- 2.500ms
Duty+ 65.7%
Duty- 33.8%


20k RPM

Code Select Expand


CH1 20.0mV  5.000ms 10.00kSa  [Date:2/12/2009]

Vpp 44.0mV
Vmax 28.8mV
Vmin -14.4mV
Vavg 3.89mV
Vamp 45.6mV
Vtop 29.6mV
Vbase -14.4mV
Vrms 12.8mV
Vover 39.6%
Vpre 5.26%
Frequency 270.0Hz
Rise Time 2.300ms
Fall Time 900.0us
Period 3.800ms
Pulse Width+ 1.300ms
Pulse Width- 2.700ms
Duty+ 32.4%
Duty- 66.7%


The frequency is quite interesting, also the duty cycle seems be inverted from 10k to 20k. If I take the Dremel tool and go horizontal to the cow magnet it generates a lower voltage but is like a distorted square wave. Have to play with it some more.

[Paul-R]

With big magnets and big coils and high speed, this should really be neat.  Also, I think that the fellow said that his output was AC, but I might be wrong.  Does that make sense? 

Yes. I tried a simple slow running set up, and my Avometer did not follow the changes when set to DC. I speeded up the rotation, set
the meter to AC, and the voltage was fluctuating but consistent.

There is something very interesting about this idea.

Paul.