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Homework Help: BEd degree - magnetic generator - help with design

  1. Jan 6, 2012 #1
    Hey guys - I am doing my BEd degree. I'm going to get this out there right off the start because it will save a lot of issues. Please don't take this the wrong way, it's simply the truth as I know it.

    I am doing my Bachelor of Education, to be a teacher. As a teacher, based on my 'teacher training' I know that I do not know everything, nor should I be expected to know everything. It is expected and in fact highly encouraged to seek out information from people - such as the people on this forum - when I do not know the information. The reason is simple. My job is to teach. To teach the best that I can teach would mean that I would teach things that I did not myself learn the 'hard way'. And when that is not possible, because I physically can not learn that amount of information in the amount of time required, then it is expected, and encouraged that I seek out someone that does know the information that is required to teach the students.

    This is the truth.

    I know it seems counter intuitive to what this very section of the forum stands for. But it is a reality.

    To those people that still disagree because you have spent hours studying to know what you know - and again I am not saying this to be rude or argumentative, simply to get to the point and support it the best way that I know how - I ask you this: if you went to someone for knowledge, say at a university, have you never seen them have a 'guest lecturer'?

    Believe me I have put in the hard work to get where I am. It's just a part of being a teacher though - getting information from others.

    The obvious reason for that speil is that I need information, and it makes more sense to get it out in the open at first instead of going in circles of having people insist that I learn things the hard way before teaching them.

    1. The problem statement, all variables and given/known data

    Create a resource that can be used to teach science or social studies to children grades k to 6 based on the Ontario Curriculum.
    Should not copy something that can be readily bought. But the content and ideas should be drawn from a range of sources - which should be acknowledged in notes.
    It promotes effective teaching and learning (based on research).

    My choice is to show how energy can be created. I have managed to get a working kelvin thunderstorm. But it seems a bit finicky and I might switch to my original plan which was to have a magnetic generator

    2. Relevant equations

    The simple part - move a magnet over a coil and you get energy. Alternate north and south and you get alternating current.

    Coil wrapped on conductive material

    right hand rule - wrap in the direction of the right hand fingers to have a flow in the direction of the thumb.

    I am using magnetic wire - I think 32 guage.

    3. The attempt at a solution

    I originally was going to use water to turn a wheel that would turn a magnet to create energy. That failed miserably because I spent more time building the contraption and less time on the actual design of my generator.

    I first made a circle with various posts around the circumpherance of the circle. Each post was wrapped the same direction (I now think this is where I went wrong with that, the other issue was that my centre piece was made from wood, and not a conducting material). All my posts were perpendicular to the magnet. I lined up my magnet in the middle and hooked up a volt meter. I got nothing. Even tried it with a drill, still nothing.

    I then tried wrapping nails that had been taped. This managed to work but only with an electric drill. Using a drill is not really going to cut it for myself because I want the students to ideally be able to generate electricity with their own power.

    I have found this link on you tube that utilizes a lot of wire with magnets routating in the middle to generate enough electricity to power a small lightbulb.

    This shows that it works. I could easily just copy this method, but I really want to try to get something more efficient.

    What I am looking for is a way to utilize magnets - I have four rectangle dipole magnets (same size), two Prolate spheroid magnets with the dipoles on either side of the minor axis, and 3 stereo magnets of varying sizes - to create enough energy with human powered movement to light an LED, or several.

    The video looks inefficient. To me it would make more sense to have the coils on the outside of the magnets, like I had done originally, to get the most amount of wraps out of the available wire.

    Can anyone either help me in my design so that I can figure this out, or direct me to information that would have what I am looking for?

    Most of what I can find is either too simplified, or over complex.

    I think to get it to work I need to have my posts parallel to the magnets as they rotate, such that they are outside the diameter of the rotation. They need to have a metal interior to allow for an even distribution of flux, but with tape on the layer that touches the wire (not sure why the tape needs to be there).

    I think the rotation needs to alternate between each post. But I am not sure if that is the case or not.

    I also need to figure out the necessary pattern for a given post count. and to know where to have my circuit exit and enter the posts.

    I could be missing something completely that would be way easier. If I am please don't hesitate to offer an alternative suggestion.
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Jan 6, 2012 #2
    One thing I am thinking of is using my 4 magets set in a circle. With armature on the inside and on the outside of the circle. it will be a pain to build, but I think it would have a more steady flow and have less interference.
    I could be wrong though.
    If I set them all together such that the 4 n's were facing one way and the 4 s's were facign the other, I think I would have more interference and would loose energy.

    What do you guys think?

    Does any one know anything about winding design? Or where I could find decent information on it?
  4. Jan 8, 2012 #3
    I think you are trying to make a permanent magnet synchronous generator with the permanent magnet as the rotor. I am not an expert in generator design.

    rotor = rotating part
    stator = stationary part

    I think ideally it would be a high permeability material. You can buy "cores" for this purpose.

    The configuration is not ideal. It might be better if the posts were parallel to the magnet. There are multiple configurations that may work.

    You may think of the magnetic field (B field) as something which goes out the north end of a permanent magnet and into the south end. Basically, the rate of change in the amount of this field going through hole in the coil is what matters for determining the voltage on a voltmeter. That is, in terms of what the permanent magnet does; there are other considerations like number of wraps.

    In the image below, you can see how a design has a ring of material on the outside that is like a conduit for the magnetic field. This would be a high permeability material. This feature doesn't seem to be present in your design.

    EDIT: In the design shown below the armature coil is wrapped around the rotor itself. This may be superior to the Stanford link for educational purposes, because it shows a magnetic direction switching inside some loops of wire.

    Also, make sure your voltmeter is in AC mode.

    If you have a data sheet for any of your permanent magnets, maybe you should make an estimate of output voltage magnitude based on RPM, number of turns, core material, and estimated flux linkage (maybe just assume perfect linkage and expect some percentage of that). This way you might have an idea of how to set the voltmeter, and that your device would produce a reasonable voltage.
    Last edited: Jan 8, 2012
  5. Jan 8, 2012 #4
    Could have sworn I uploaded a pic.

    I am changing my design.

    I've got a one phase 20 pole generator I'm working on. The windings will be perpendicular to the magnets in a circle. So the magnets will run directly over top of the windings. Alternating N/S around the circumference.

    Similar to this design found here:

    Except my design has the magnets over the windings.

    Below each of my windings I have steel wire wrapped around to act as a core/stator to allow for the flow of flux between windings.

    I'm doing 100 wraps per winding. With 32 guage wire. And only using ceramic magnets.

    The windings are fairly tight. about 12mm in diameter.
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