Switching permanent magnet field

Discussion in 'The Projects Forum' started by don'tknow, Apr 8, 2015.

  1. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    About this video, one thing that confuses me is, at the beginning (without the power supply.) why the El.magnet on the right (our right ) does not attract when power off ? , while the other one on the left does .
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I speculate that once the magnetic circuit on the left is completed, the remaining field that is not in that circuit is greatly diminished, so there appears to be little attraction left to attract the second core. This would be true of the circuit was first made on the right, but he doesn't show that example.

    Pulsing the the coils causes the PM to jump to the polarized core, and this can cause a toggling of which core the PM adheres to.
     
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  3. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    Thank you for your reply . I have to try this to be sure what' is going on in there . I always thought that the attraction would be equal on both sides. one more question , ( while power off. ) does the wire helps there ? or that circuit only needs the core to act the same ?

    No need for this answer , i think i got this now. Thank you. :)
     
    Last edited: Apr 8, 2015
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    I used to have a keyer with a set of paddles ( for sending morse code) that had permanent magnets instead of springs. there were u shaped brackets mounted to screws with knobs that moved to cover the magnets to adjust the field. you can put a shunt across the poles of a magnet to make it let go of whatever. also, a shunt should be used when storeing magnets.
     
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  5. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    thank you. Actually I had more questions before i made this thread .. and i forgot while making the thread.. poor memory . now. with a stronger magnet .. more current is needed right ? and what if I have less wire than the coil on the video, what do i have to increase to get the same effect in switching the field ?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Also when you attached the magnet to the two steel bars, they in turn became magnets.
    You should also experiment with a steel bar with no P.M. magnet involved and see the different effects.
    Lift magnets on cranes etc run into this phenomenon and steps have to be made to de-mag.
    Max.
     
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  7. wayneh

    Expert

    Sep 9, 2010
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    Field strength depends on amp-turns. More turns increases the field, but at some point can increase the DC resistance so much that the current goes down. Calculating the optimum wire gauge can be a challenge. You also have to worry about heat generation.
     
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  8. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    Thank you all. I think that's about it for now . is there any simulation program where we can have simulations of physic laws installed, where i can create (for example circuits boards .. and experiment with electricity , magnets and wheels.. etc. ? if not it would be great to have one . :) respec.t
     
    Last edited: Apr 8, 2015
  9. wayneh

    Expert

    Sep 9, 2010
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    The favored electronics simulator is LTspice, because it's free and works well. But it won't help you much with more physical stuff.
     
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  10. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    Thank you . I will check that one out . if there is a better one with more possibilities it is no problem to pay for it. i would love to see that one too. The one with almost all the possibilities would be great, from gravity , weheels, generators .. windings.. wire thickness , magnets . . someone could be a new millionaire if he makes that. :) respect
     
    Last edited: Apr 8, 2015
  11. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Sigh!!!:rolleyes:

    I thought we had this all out in PM???

    Here's a re-post of my reply to your PM
    ==========================================================
    My impressions of the video...

    FWIW --The electromagnets are fashioned from shaded pole ('skeleton') motors.

    Owing to the 'inverse parallel' connection of the windings, the electromagnets act in opposite 'directions'...
    Thus when the yellow lead is positive the electromagnet to the viewer's left 'opposes' the PM's field with the result that there is little to no attraction, or, even, repulsion (dependent upon the relative field strengths) -- while the electromagnet to the viewer's right, owing to the 'aiding direction' of its field, more intensely attracts the PM --- The converse being the case with reversed electrical polarity...

    Of course when the electromagnets are not energized the PM equally attracts each electromagnet (all else being equal) owing to ferromagnetism...

    Please note that there is nothing 'fringe' about this, in point of fact this principal has been used for decades (in such applications as 'fire-door closers', 'buzz-through' security locks, some light duty EM cranes, arcade games , etc...)
    ============================================================

    With somnolent regards
    HP
     
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  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Mine are all 100amp!:oops:
    Max.
     
  13. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    yes we did, but power off confused me. i thought it must attract the other one too.. when power off. it's all good now. ;)
     
  14. Hypatia's Protege

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    Mar 1, 2015
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    I've seen crane magnets (at salvage operations) powered by DC generators the size of 55 Gal. drums!:eek: --- Of course, in so heavy an application, any reverse permanent magnetic 'bias' is merely to overcome residual magnetization and, hence, assure attainment of (effective) 'zero flux' sans reversal of electrical polarity...

    Best regards
    HP

    PS --- Golly! Now I've gone and referanced the unit 'gallon' on an INTL. site!:( --- I must take 100 lines...;)
     
  15. Hypatia's Protege

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    Fair enough! :D:D:D

    Best regards
    HP
     
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  16. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    what is needed for the poles to be switched from N S to S N ? hehe.. never mind that. more important , if i wan't it to switch left and right very fast , will increasing the voltage help in speeding up the switch ?
     
    Last edited: Apr 11, 2015
  17. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    no, the speed of switching between the two coils is determined by the switching speed of the applied voltage, so use low frequency AC., bigger voltage means bigger magnetic fields.
     
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  18. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    Thank you. appreciated :)
     
  19. Hypatia's Protege

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    What exactly are you trying to do? 'Cutting to the chase', as it were, is often the best approach...

    With friendly intent:)
    HP

    PS
    FWIW I'd use an 'H-Bridge' arrangement...
     
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  20. don'tknow

    Thread Starter Member

    Feb 5, 2015
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    trying to find out more about this world I'm being made off and live in.. ;) just experimenting with stuff, nothing special .. It helps me understand things better .. idk.. I hope that's ok ?
     
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