Solenoid

Discussion in 'General Electronics Chat' started by Robin Hooper, Apr 3, 2006.

  1. Robin Hooper

    Thread Starter New Member

    Apr 3, 2006
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    Just a general question at first since I'm not positive if a solenoid can retain its characteristics if it was shaped in a "C" shaped channel. Can a ferrous material travel along its length if a current is passed through the coil? Or would the plunger tend to be pushed out instead of along the channel. Constructing the wire in a "C" is another matter all together for me but for now I would like to know if it is at all possible?

    Thanks
    Robin Hooper

    Oh, I best tell you all that I'm a Cabinet Maker and not an electrician or an electrical engineer.

    Thanks Again.
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    The action of a solenoid to move back and forth along an axis REQUIRES that the wire form a series of concentric loops. That way the magnetic fields add up into a larger field which moves the plunger. If the wire is wound back and forth in the shape of the letter C then the fields in each part of the "C" will cancel each other for no net force, or maybe a very small force from the odd winding.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
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    Sounds like a torroid core with a chunk taken out of it. Might work, but mechanically very challenging.
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    That's great, but the field in a torroid is inside the torroid. Pretty tough to move a plunger inside a torroid, or am I missing something. A picture or a diagram would certainly be helpful here.
     
  5. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    Only having a guess here but I think that in on direction of current flow (because there is only half a core) that the plunger will be attracted to the core. In the other direction of current flow the plunger maybe thown out of the core.

    May we ask why you only have or want a "C" shaped core?
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    Would somebody please post a picture. No two of us has the same picture in mind.
     
  7. Robin Hooper

    Thread Starter New Member

    Apr 3, 2006
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    Thanks for all your input

    To clarify things a little, picture a 1/2" copper pipe 12" long with a slot cut out of it along its entire length, now substitute the copper pipe with magnetic/motor winding wire that is hooked up to an electrical source. Place an iron rod into the hollow of the copper pipe/wire coil and turn the electricity on. Will the rod move along the length of the pipe and perhaps shoot out of the other end?

    Here's my reasoning, keeping mind I'm a cabinet maker ok guys. If this can be done it should be possible to form the C coil channel in a complete loop, yes looping back on itself, forming a circle, a hollow dough-nut whereby the interior of the dough-nut will now house the iron core(s). Turning the juice on should cause the iron core to travel in circles. I hope I haven't lost any of you. I can draw a picture of it but I'll need some advice on how to upload it to this forum. I understand that not using a C shape and instead taking a conventional coil design would be much easier but this won't suit my purpose. Eventually I will need to mount a propeller or better yet an auger in the center of the dough-nut. The iron cores will then be mounted on the extreme outside of the blades. I'm trying to design a different type of motor, whereby the the force that turns the props/auger is not from the center shaft. It takes allot more torque/energy to turn something from the center than from its perimeter.

    Thanks for your input
    Robin Hooper
     
  8. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    Unfortunately, if I have pictured this correctly, if you fold the coil back on itself the magnetice flux will be equal and opposite in each half of the coil. This will cause it to cancel the magnetic force with a result of zero.

    This is assuming I have got it right. You will have a piece of wire going from one edge of the C channel to the other edge then folding back and going back to the first edge. This being repeated over and over again.
     
  9. Papabravo

    Expert

    Feb 24, 2006
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    As I said in my original reply the only possible force would come from the odd run of wire since all the pairs will cancel each other. The magnetic field in a current carrying wire circles the wire. The magnetic field exerts a force at right angles to the moving charge. There are no cicumstances under which a solenoid type winding can create an angular force. What you will end up with is a solenoid with a fractional turn which will exert a force along the axis of the cylider.

    Look at a diagram of a three phase brushless motor.

    Brushless DC Motor App Note

    Let us use a cylindrical coordinate system. Let small r be the distance from the center of the rotor shaft. Let the greek letter theta be the angular position. Let small z be the dimension going into and coming out of the page. Using a rotor with permanet magnets the coils on the stator go in and out of the page in the z direction. The magnetic field lines in the CENTER of each stator winding are in the r direction. When a wire carries current to produce a field the force is in the theta direction and the rotor moves in the theta direction.
     
  10. dtiger2k

    Member

    Mar 29, 2006
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    I am assuming that this is some what similar to what your talking about. I have to agree that this would never work as your thinking it would. Also, as you were stating about cutting a slot in it for the fan to ride in you would completely kill the whole coil effect anyway.



    [​IMG]
     
  11. Papabravo

    Expert

    Feb 24, 2006
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    See the problem. Go back to the description.

    1/2" diamter
    12" long

    A slot is cut along the 12" dimension. There was no mention of bending the the tube into the shape of the letter C. Only the partial turn of wire from one side of the slot to the other looks like the letter C.

    Wires go from the edge of the slot sround the 1/2" diameter to the other side of the slot. Then they reverse direction, go around the 1/2" diameter to the starting point. This action proceeds from one end of the twelve inch length to the other.

    If the number of partial turns is even, you ended up on the same side of the slot as you started, then the net magnetic force is zero!

    If the number of partial turns is odd, you ended up on the opposite side of the slot as you started, then there will be a small magnetic force along the 12" dimension. Nothing inside the tube will have any motivation to rotate.
     
  12. Robin Hooper

    Thread Starter New Member

    Apr 3, 2006
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    Well back to the drawing board. That was an awesome picture of what I was thinking. Thanks for being patient with a guy that wants to know but is just at the beginning.

    Can any of you give me a reference(s) in learning all there is to know about induction? Ok,ok just an intro will do for now. LOL

    Robin Hooper
     
  13. dtiger2k

    Member

    Mar 29, 2006
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  14. Papabravo

    Expert

    Feb 24, 2006
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    Try this link

    Solenoid Behavior
     
  15. windoze killa

    AAC Fanatic!

    Feb 23, 2006
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    I just thought of another way you could do this. A lot of horseshoe electro magnets along the length. That way the tips of your propeller can pass through the magnet poles and be forced on. I am just trying to conceptualise how to draw it. I will see what I can come up with tonight.
     
  16. thingmaker3

    Retired Moderator

    May 16, 2005
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    Another option might be to build a series of rail-gun type rails. They would have to be very precisely made (cabinet maker's skill could come in handy) and form a circle with breaks in it.

    One could also build a windmill type alternator and drive it as a motor. This would be "inside out" from Windowz Killa's idea - permanant horseshoe magnets on the fan blades moving past fixed flat electromagnets as they are sequenced.
     
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