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magnetic switch/connector

Discussion in 'General Electronics Discussion' started by agilbert, Apr 27, 2017.

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  1. agilbert

    agilbert

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    Apr 27, 2017
    Hi everyone,

    I have a specific scenario in mind, and I can't find any component that I can just buy to fulfill my needs.
    So basically what I want is:

    When two magnets are together, the current pass.
    When the two magnets are separated, the current doesn't pass.

    (5 volts)
    I want to have a "magsafe" feeling, so the magnets should not be very strong.

    The first idea I had was a "magnetic connector", just like the magsafe, but it would just let the current pass through the wire when the two pieces are joined.
    something that would look like this:
    http://www.rosenberger.com/images/de/products/medical/powersystem_2015.jpg

    The second idea I had was a "magnetic switch".
    (I joined an image of what I have in mind)
    So the yellow thing, is a spring that push a cylinder magnet up in the tube.
    when another magnet approach, the magnet goes down in the tube, making the connection at the same time, and the two magnets "clip" together.

    I can't find any similar component on ebay.
    Maybe I'm not searching for the right terms.
    If anyone could help me find what I'm looking for, I would be so thankful !
    Or if you have better solutions, I would gladly take them as well :)

    Thanks in advance.
     

    Attached Files:

  2. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    I would use one magnet and a reed switch.
    A reed switch is a sealed glass tube filled with a vacuum or inert gas. It has a two reeds fitted, one from each end. When a magnet is near, the reeds are pulled together, completing the circuit. The reed switch is only suitable for low current switching.
    These are used for window alarms etc. I have used one to monitor a large shaft running at up to 1000rpm.
     
  3. agilbert

    agilbert

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    Apr 27, 2017
    Yeah, I'm aware of the reed switch, but I really need the two parts/magnets to clip together (and let the current pass).
    I was searching for "magnet(ic) reed switch" or "two magnets reed switch" or "magnetic reed connector" without luck !
     
    Last edited: Apr 27, 2017
  4. davenn

    davenn Moderator

    13,673
    1,892
    Sep 5, 2009
    and how are they going to separate once they are stuck together
     
  5. Externet

    Externet

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    Aug 24, 2009
    Magnets wrapped in copper foil. Wires soldered to the copper.
     
  6. agilbert

    agilbert

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    Apr 27, 2017
    Like a fridge magnet, when I take it with my hands and separate them !

    I'm not sure to understand what you are saying. Can I buy something already built ? Or do you have a DIY web link ?
     
  7. Externet

    Externet

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    164
    Aug 24, 2009
    Never seen such already built, but where is the mystery ?
    Or a cylindrical magnet that fits inside a piece of copper pipe. Two of them. They will still attract/repel.

    Wires soldered to each copper pipes will
     
    agilbert likes this.
  8. agilbert

    agilbert

    4
    0
    Apr 27, 2017
    Oh ! I see what you mean. but yeah then I can't completely separate the two parts. Since the wire is soldered to the two cylinders.

    Actually, I have a friend who told me I could just glue a "metal piece" to the "reed switch", so the second part (the magnet) would stick to it !
    I'll try this solution.

    But yeah thank you @Externet for your good advices :)
     
  9. Bluejets

    Bluejets

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    Oct 5, 2014
    Metal part glued to the reed will probably shield against the field and hence be a flop.
     
  10. Externet

    Externet

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    Aug 24, 2009
    Yes, you can separate them. Each copper 'wrapper' has its wire.

    Wire1------------------------------------[magnet]/[magnet]----------------------------------wire2
     
  11. ChosunOne

    ChosunOne

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    Jun 20, 2010
    A magnetic SPDT reed switch attached to a magnet with a spacer between them, with spacing calibrated so that the magnet just barely activates the switch. Do do this, hold the switch in place while you inch the magnet s-l-o-w-l-y up to it. When the switch engages, that's the space you want between them. Find something that thick to put between the two for a spacer and bind them with glue or a rubber band, or whatever.

    When you bring a second magnet up to the activating magnet, with polarity reversed to "clip" to it, it diverts/collapses the magnetic field so it's no longer strong enough to keep the mag switch activated.

    I've had to do this before. It works, but be meticulous with your spacing.
     
    duke37 likes this.
  12. Bluejets

    Bluejets

    4,290
    911
    Oct 5, 2014
    A properly placed dc relay coil will do the same. A trip mechanism widely used inside earth leakage safety switches.
     
  13. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    Tou may not need a second magnet. A lump of old iron will shunt the magnetic field and release the reed switch.
     
    ChosunOne likes this.
  14. ChosunOne

    ChosunOne

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    98
    Jun 20, 2010
    That will work too--and old nail or bolt, cut short enough to cling to the magnet.
     
  15. ChosunOne

    ChosunOne

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    Jun 20, 2010
    I just had a thought I ought to share: A common source for magnetic reed switches is the alarm industry stores. If you're buying from any kind of alarm supply store, be aware that in the alarm industry, the NO and NC designation for reed switches is different from standard electronic nomenclature.

    In alarm-speak, a reed switch used to sense an open door or window is "NC", meaning that the switch is closed when the door/window is closed. The door or window sash is fitted with a magnet that is brought into proximity of the switch when closed, so that the magnet closes the switch. In alarm-speak, "normal" means the state of the switch with a door/window/vent/whatever closed. In standard electronic nomenclature, we call that switch NO, the state it's in with no outside influence (such as a magnetic field).

    This is why I specified a SPDT reed switch, to ensure you have the switch you need regardless of nomenclature confusion.
     
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