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Faraday Induction Generator

  1. Mar 9, 2005 #1
    Hi i was just wondering if anyone would be able to help me...I am planning on making a faraday induction generator for a science project...I was thinking of using 1" ID pvc tubing open at both ends....I have a couple rare earth Neodymium Iron Boron magnets that i will place within the tube, and close the ends of the tube with springs at each end...The magnets will be oriented so that the poles will be in line with the openings of the tube...I then wanted to wrap bare copper wire around the tubing and then connect the wire to a light bulb socket with bulb....my hope is to see that as the magnets move back and forth through the coils that there is a current being produced in the wires thus causing the lightbulb to illuminate...
    My main concerns is first making sure that this will work, and what type/ guage of copper wire I should use as to get the best results...Will any watt lightbulb work? Also I wanted to study the effect of changing the number of loops in the coil as well as changing the number of sets of coils...what would be the best way to quatify the change? Thanks alot for any and all help...Omar
  2. jcsd
  3. Mar 11, 2005 #2
    Omar , this sounds like a fun project, but to start with , if the poles of the magnets are inline with the opening of the tube it will not work .. because the magnetic flux has to cut through the coil windings..what shape are your magnets?? dimentions?
    also , to get it to work the north pole of a magnet has to cut through one side of the coil , while ,at the same time , the south pole cuts through the other side..
    besides that , It is a very good idea and would work , if your poles were facing out of the side of the tube..
    since you are more interrested in voltage at this point ( although you will also need current to light the bulb , but not much) i would suggest enamel coated " magnet wire" if you want to experiment with some there is a lot in the deflection coil of a TV or a old PC monitor..
    also the bulb can be ordered from jameco electronics ( they have one that only requires 40 or 60 mA to light ..) good luck..
  4. Mar 13, 2005 #3
    This link (http://www.foreverflashlights.com/ ) describes a shaker flashlight which uses the principle you describe. It uses an LED, as an incandescent lamp needs too much energy to make it practicable. Buy one and operate on it to get ideas.
  5. Mar 14, 2005 #4
    Thanks for the great advice...I actually have a couple different sets of magnets that I am using...But since you are saying that I have to have the poles in line with the sides of the tube i will probably use two spherical magnets with a .75 in diameter....I was thinking in order to keep the magnets in the correct orientation i would use the second magnet outside of the tube so by moving the magnet outside of the tube it will cause the magnet to move within the tube...Since it is a sphere it will be able to roll within the tube while keeping the correct orientation...The other magnets I had were 0.500" Dia [0.135" ID] x 0.250" Thick NdFeB Ring Magnets...I ordered all my magnets from Amazing Magnets...and boy are they strong...The ring magnets are really tough to get apart once they are together...
    So you suggest using "enamel coated magnet wire" what makes this better than bare copper wire? I was just wonering because it seems like most applications use bare copper wire...plus bare copper wire is fairly cheap and easy to come across...If I didn't want to break a tv or monitor...where else could I get enamel coated magnet wire? is it something you could get from Home Depot?
    Thanks for the input about where to get the light bulb...I was thinking that it was one of my problems that I was using too big of a bulb...I took a look at the sight jameco electronics, but I wasn't sure which bulb you were talking about... I was just thinking of hacking an old flashlight to get the bulb and socket...that should work ....right??...Hopefully I will have a working model by the end of the week...thanks again...Omar
    Last edited: Mar 14, 2005
  6. Mar 14, 2005 #5


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    Bare copper wire is NEVER used. It appears bare because it has a varnish type coating. Try Radio Shack?
  7. Mar 14, 2005 #6
    Aww...I didn't know that...thanks...
  8. Mar 14, 2005 #7
    Doctor2B you need to orientate the poles so that the flux exits the side of the tube( where your coils are wound ..) the best way to do this would probably be to hot glue a smaller tube on either side of the magnet ,,inside the outer tube, . this way the magnet has no choice but to present the poles to your waiting coils..
    you could even use both magnets ,and see how the orientation of the magnets changes the amount of current produced..by orientation i mean the poles allways pointing out , but rotated around the tube..
    i would suggest using the thinnest wire possible, within reason , because you will need a lot of it..
    as i think of it two springs , at either end of the tube , two magnets seperated by a thinner tube , all inside a larger tube would be perfect.. :smile:

    this is a link to stuff i have done , and am still working on..
    its a long thread but the link should take you right to page six 1/4 way down is a pic of one my generators..
    Last edited: Mar 14, 2005
  9. Mar 15, 2005 #8
    somehow you have to prevent the magnets from sticking to the springs, and it should work..
    maybe if you let the springs attach themselves to the magnets , they might even stay put..
    but in either case a smaller tube is essential , even with one magnet ,for reasons stated earlier..
  10. Mar 15, 2005 #9
    Thanks for the advice...what are you using to measure the power output of your generators?? I have actually thought of a way to not even use springs at all...As for the smaller tube within...I think this would not be necessary beacuase outside the tube I have an identical magnet fixed approximately .25-.5" away from the tube....at this distance the magnetic force is strong enough for the outter magnet to pull the smaller magnet through the tube...Since the magnets I am using are spheres they are able to roll about one axis while still presenting their poles to the coils..
  11. Mar 15, 2005 #10
    yeah but your coil will be on the outside of the tube..and you have to move the magnets really fast past the coils to get any voltage to speak of..so shaking the tube back and forth is what you need to do to make it work..thats why the springs..i have a voltmeter and a scope..i usually use a one ohm wire-wound resistor when measuring the output..
  12. Mar 21, 2005 #11
    I have a quick question about the wiring of the coils...As it is right now I have one end of the coil taped down to the tube...and the other end of the coil is attached to the positive terminal of the bulb...is this right? or should one end be at the positive terminal while the other is at the negative? thanks for your help...Omar
  13. Mar 21, 2005 #12
    if you dont connect both wires to the buld how is it going to work??
    a bulb doesnt care which terminal is positive or negetive
  14. Mar 24, 2005 #13
    i had some free time last night so i made a shaking tube magnet generator..
    i have a 1'' od. clear plastic tube with 5 ( 1.0 '' x.5 '' x.125 '' )magnets inside ,they fit nicely..with a "lot" of wire wrapped around it ..
    well the results are less than spectacular.
    i know if i had that much wire in a coil , with the same magnetic flux , hooked into my home made generator that i would get at least 5V from it without even trying..
    so therefore , something is cancelling out.. , but what??
    i hooked up two diodes anode to cathode in series with a 100 ohm resistor across the terminals of the coil..
    i cant see the difference between two magnets north and south facing a coil , passing over the coil ..and essentially one magnet north and south passing through the center of a coil..???
    i cant figure it out..
    Edit :: right hand rule ??
    maybe i need two coils ..
    Last edited: Mar 24, 2005
  15. Mar 25, 2005 #14
    i have made a considerable amount progress.. :smile:
    the diodes now blink reliably..
    it was the orientation of the magnets that was the problem..
    i also have 1/2'' diameter x 1/2 '' long magnets , and i am using five alltogether , no springs either , because i put one on either end in place of springs..
  16. Mar 25, 2005 #15


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    I have seen those 'Forever FlashLights' advertized on TV, and I thought they looked pretty interesting but I couldnt figure out how they worked, I knew it must have had something to do with a moving magnet, but then I decided to put some brain power into it, and this is what I camp up with, which might also have some usefullness to what you are building.
    I figure they have a magnet in a tube with coils all around it (just like what your doing), and then you shake the flashlight/tube to move the magnet and induce a current, storing this electricity in a capacitor until the switch is turned on, but wait! if you shake it then the magnet will move both "up" and "down" the coiled tube, inducing current in both directions, and if you do this then it will cancel out the charge stored in the capacitot (when it moves up it makes the charge, moving down removes it). So how did they keep it from doing that?
    This is what i came up with.
    They have 2 circuits, one for when the magnets goes up and one for when it goes down, both connected to the capacitor storing the charge.
    but the catch is that the put a diode in between, and as is my understanding of a diode, it will only allow the charge to flow in one direction, creating almost no resistance in the circuit one direction and almost infinite in the other direction. so this solves the problem, each shake further charges the capacitor, and then when the switch is flipped, the capasitoris discharged.

    What do you think, does this sound right [everyone]? Or if it is not, would this idea even work? I think it sounds like a good idea.

    One other thing that I think would be cool, to insted of having a moving magnet you shake to move through a coil of wires, have a coil of wires you shake and move it through the Earth's magnetic field, although it would take considerably more shaking to build up enough charge. (using the Earth's magnetic field against it [how it is being used against the Earth, that is your job])
    Last edited: Mar 25, 2005
  17. Mar 26, 2005 #16
    your idea of using a diode is right on the money..
    looking at the wave on a scope the main peak is positive when the magnets move in one direction and when they bounce the other way the main wave is negetive..i am currently using a bridge rectifier and a step up transformer , and am getting a little over 20 V peak at 3mA..before i was using the transformer, i was only getting about 3V peak at 11mA..
    the problem is the diodes use over a volt to turn the low voltage (higher :rolleyes: current ) into DC..
    As for a capacitor, the one i tried was in the uf range ( too small) but it did work. It stored enough energy to keep a large LED going for a split second till the next pass of the magnets...
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