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Forum Index : Windmills : PMAs for Beginners
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yes thats not going to work. The magnet must pass over the center of the coil, and the center of the coil needs to be bigger than the magnet diameter for best results. So the magnet passes over one side of the coil, its direction of travel is at right angles to the wires, it hten pases over the center of the coil, where there are no wires, and then over the other side of the coil. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=mulligan] . . . does anyone have their own design or configuration for a mini PMA . . . As a matter of fact, yes. If you can wait until I get around to it, I have designed and partially built a very small (like 60 watts output) axial-flux alternator that can be made with the only fancy tool being a drill press. It is a true axial-flux, the main shaft is a front bicycle hub and the magnets are small, round neodymiums that I purchased online for around $0.50 each (although, I bought a suitcase full!). Sooner or later you'll figure this out, so I may as well tell you right up front that I build what most here would call "toys". They work (well, not always, but often) although they are meant to do no more than put a "topping charge" on 12-volt batteries. I live on my land yacht and have reworked all my elecctrical needs around having a 12-volt lifestyle. In fact, I even put up a post HERE with that title. Another thing I might as well tell you is that I am much, much better at "starting" projects than finishing them. To that end, just be patient and hang in there. If you're about to fill yer pants, PM me and I'll get you headed down the right pathway prior to my posting the build for the rest of the crew here. Be assured, however, that I will eventually get around to it. . . . . . Mac 
Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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niall1 Senior Member  Joined: 20/11/2008 Location: IrelandPosts: 331 |
the plots beginning to thicken now...and its certainly confusing me ... 
at right angles to the coil legs it seems ideally a n..s through one leg and s...n through the other.....a complete circuit ?..then reverse the (flat top and bottom) of the coil dont add anything...(they arnt cut) but according to Hughs diagram it seems more to do with a growing/collapsing field through the coil center and then quickly reversing polarity cycle... maybe thats actually the same thing....? ....i know this subject has come up before with regard to how transformers work .....it does make you think never a dull moment then ....  ...thank god for that niall |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
niall1 On closer look, I see where the confusion likely lies. In the picture, Hugh shows a crank on the end of the horseshoe magnet. Turning it would accomplish the desired task, but I think the ends of the magnet would necessarily have to pass beyond the circumference of the coil (otherwise it would mash into it, eh?). If the north face travels in a downward direction past the coils on top, while at the same time the south face passes the other leg of the coil on the opposite side in an upward diretion, this would induce a current into each leg and that current would flow in the same ELECRTICAL pathway inside the wires, so it would work fine. Look at it carefully, then compare it to that simplistic picture back a page in my post and you'll see it's perfectly correct. (I think  )
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
i see your point Mac.... but this is the bit that confuses me ...
take a regular old car ignition coil ...its got one round coil that's got a heavy winding and a lot of finer (lot more turns) wrapped around it ...the heavy coil is fired by the engine points creating a magnetic field ... this field collapses when the points open ....but the finer windings pick up on this collapsing field and generate a very high v for the spark plugs nothing in it seems to have a 90 degree attack angle (my confusion .. )...both windings are round and wrapped around each other ...but yet ..it works ...
a perfect high kv generator ... or is it ?....got to be a simple explanation ...
sorry Mulligan for going off thread.... niall |
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| mulligan Newbie  Joined: 26/09/2011 Location: United StatesPosts: 10 |
Wonderful. I am getting answers I would haven't found elsewhere, a true internet success. Niall1 I put together the small axial cardboard generator you sent a link to, and with 20 3/4" ceramic round magnets and a little over 200 turns of 30 gauge I was able to put off around .3-.7 volts AC. Woo HOo! Free energy! |
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Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
niall 1 Hi, niall 1 wrote,, nothing in it seems to have a 90 degree attack angle (my confusion .. )...both windings are round and wrapped around each other ...but yet ..it works ... The Field is made to move Electronically, A Magnetic field that changes intensity in the presence of a wire/Coil will cause a current to flow in the wire. A magnet approaching and leaving a coil of wire, either across its turns or through its center is changing its intensity with respect to the coil(the Distance Changes). A magnet face rotating above a coil face has a steady field value and the distance does not change. No Change, No Juice! The auto Ignition coil is a variable frequency transformer,Its principle of operation can be described as a small engine and gearbox connected to a very strong spring and is stretching that spring slowly (distributor points or solid state switching connected to the coil primary winding, The current flow here begins to magnetize the Iron core in the coil. this is quick but still requires a few micro seconds to establish full current flow because of impedance.When the Spark timing is right The points or switch break the circuit from the Battery.The big spring is released,(Magnetic field,) The collapse of the field is near the speed of light.From Max intensity to 0. This quick change in field strength is the motion needed to induce a very large voltage in the many turns of the Coil Secondary Winding. The small capacitor used with the coil enhances the output. -------Cheers, Roe Time has proven that I am blind to the Obvious, some of the above may be True? |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
thanks for that explanation Greenbelt.. "made to move Electronically" is a nice way of putting it ...i got stuck in a physical movement way of thinking about it .. 
you might be able to put your alt to work to earn its keep Mulligan...it should be able to light up a light emitting diode....these only conduct (light up) when the current flows through them in one direction ...you could play around with 2 of these hooked up to the coil ends ,switching the connections on the second led should end up with the 2 leds blinking alternately to reflect the ac current of the alt ...thel,y give a visual indication of the ac frequency as well wherever that old speaker came from might have some leds in it ....(if its been junked that is... .) niall |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
nail1 Greenbelt hit the nail on the head when he mentioned that the ignition coil has an iron core. An iron core of low hysteresis (magnetic memory) will hold the flux pattern within a linear column and in fact, as the field collapses, it follows that pathway and therefore actually does cross the other windings at a perpendicular or 90* angle. Where mulligan has a problem with his build, as I see it, his lines of flux are running parallel with the wires in the coil, so no matter how fast he cranks the thing, nothing is going to happen (electrically). If per chance, an established N-S or S-N flux field does pass a portion of his coils' legs at or nearly at 90*, he then will likely notice a meager current, but my advice to him is to better research this maybe by getting a school book at the library on "Basic Electricity" and read it. Maybe by the time he's done boning up on the basics, I'll have my 'off-the-shelf' axial-flux alternator done and that'll take all the guesswork out of the equation. Tomorrow, I'm actually planning to finish an air-pumping windmill and will be that much closer to building this mini ax-fx I'm eluding to, so hang in there; it won't be long now. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| mulligan Newbie Joined: 26/09/2011 Location: United StatesPosts: 10 |
New Question I've been using mostly recycled parts for my PMA and have acquired many different sized wires. Can I use varying sized wire in a single coil? Yay or Nay? |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
mulligan "Can you?" -- yes. Should you? -- not a good idea. For starters, if you use different-size wire in the same coil, it will be difficult to wind multiple coils, each of the same dimension and resistence. There's a rule called Ohm's Law and it states this: V=IR where V is voltage and I is current and R is resistence. If you mess with any one value, it changes the outcome of the equation. If you were to use wire of varying resistence (messing with the "R" value), one coil could possibly create too much current for the next coil in the circuit to handle and you wind up with a very short duration fireeworks display. It would seem to me more work to use differing wire sizes as well. While it may be all you have at hand, it would be worth your while to wait it out until you can afford to buy a roll of wire long enough to suit your purposes and of the proper size to handle the amount of current your alternator will produce. Here's hoping someone here has a chart at their fingertips, which could be posted for all to view, showing the relationship between wire size and current-handling capability. I'm guilty of using what I have on hand as well, but in my particular case, since all the stuff I come up with is in the range of "toys" I am able to get away with using small, cheap, enameled copper wire for my projects. From what I can see by the pictures you've posted, your time right now would be better spent researching this project more and doing a lot of your experimentation on paper. On paper, an eraser will become your best friend, whereas in the real world, mistakes cost money. So, in answer to your question, in short, nay. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
While I have just such a chart hanging on the wall in my shed I had gotten it from a website after searching for it at google - forgot the site though. You should keep in mind that wire current carrying capacity depends very much on how the wire is used. For example, at the extreme end, fuse wire is designed to burn through at a certain current. Any current below that can be carried by this wire with varying degrees of heating effect. Running multiple wires side by side, as in a coil, multiplies the heating effect, resulting in a lower safe current carrying capacity. Then there is external cooling, wire on a former over an iron core gets better cooled than wire over an air core. Wire that's cooled by a on shaft fan is higher rated than one without fan. It gets hotter in summer than in Winter and so on... So you see you have to look at any table and check for what conditions it has been compiled and reduce accordingly if conditions are more severe. Klaus |
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| Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
mulligan Hi, Here is a wire size chart giving dimensions in inches and metric equivalent. It also shows the ampere value that is commonly used as good design for each wire size. As others have pointed out, wire size should be constant and one piece (no Joints) in a coil. ---------- Cheers, Roe Magnet wire table Time has proven that I am blind to the Obvious, some of the above may be True? |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=MacGyver] . . . so hang in there; it won't be long now. Crew: It begins. I completed the lay-out drawings last evening and now it's just a matter of drilling some holes for the magnets, tapping some lands for all the little screws and sooner than you know it, I'll have an off-the-shelf (pretty much) axial-flux turbine (toy -- of course). This design is about as basic as it gets and should be something newbies can build with nothing fancier than a drill press. I'm going to be shooting for 50 to 60 watts, but it may surprise us, so that's yet another reason to stay tuned. When I've got it built up into a recognizable form, I'll start a new thread in "Windmills" and post everything there. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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