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reed switches

Discussion in 'General Electronics Discussion' started by foTONICS, Sep 25, 2015.

  1. foTONICS

    foTONICS

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    Sep 30, 2011
    I was just wondering,

    Since reed switches operate on magnetic fields, can they be used as a fail safe of sorts? Like with transformers or beside a conductor to see if too much current is going through it
     
  2. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi foTONICS,
    That's a very interesting question.
    I seem to remember years ago about electro magnetic forces being monopole and magnets being dipole. Or vice versa of course it was a while back.
    The EMF was positive driven and the magnet was north to south? Something on those lines.
    I would be quite happy to follow this and get reminded too.

    Martin
     
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    reed switches probably wouldn't be good for that.
    you would be better to use a linear Hall Effect device ... these have an output voltage that varies with the magnetic field strength and would be able to be fed to a comparator to produce an alarm signal


    magnets are dipole ... as far as science understands, its impossible to have monopole magnets


    Dave
     
    Martaine2005 likes this.
  4. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi Dave, hope you are feeling better and the nurse hasn't distracted you too much.
    Does that apply to an electro magnetic field too?

    Martin
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    The last nurse visit was last Monday nite, have been back at work all week, the leg is much better but not great
    still a bit swollen and a little tender ... on strong anti biotic tab's twice a day for several weeks

    Think of a electro magnet solenoid, it has a north and south pole

    http://www.bing.com/images/search?q...t=magnetic+field+of+a+electromagnet&FORM=IGRE

    they all have N and S poles

    Dave
     
  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Great to hear you are recovering. I would have kept the nurse a little longer:D
    Yes, I suppose magnetism needs both poles to be a magnet.......
    I just don't know where this monopole and dipole thing came from then.

    Possibly the 80s, CB antennas. I still have quite a few in my garage now.

    Martin
     
  7. Minder

    Minder

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    Apr 24, 2015
    Martaine2005 likes this.
  8. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Gauss's Law for magnetism, translated into English:
    There is no such thing as a magnetic monopole.

    Maxwell's Equations actually numbered around 20. Oliver Heavyside condensed them down to the fab four we know today, and basically invented vector algebra to tighten them up. This one usually is #2 on the list.

    ak
     
  9. davenn

    davenn Moderator

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    Sep 5, 2009
    probably, as yes you can have dipole or monopole antennas
    a monopole antenna would be say, a 1/4 wave vertical over a ground plane, eg a car roof


    D
     
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