Water spilled on charged magnets?

Discussion in 'The Projects Forum' started by brianllama150, Apr 12, 2009.

  1. brianllama150

    Thread Starter Member

    Nov 6, 2008
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    So I am desigining a table for fun in which the surface will be covered in paired magnets. The magnets will all be carrying a charge, and once the circuit is completed between a pair, a set of a few LEDs will turn on underneath the glass. Special cups will be designed (crappily :)) with magnets in the bottom as well, and so when it's set down on the table and connected to the magnets a light will shine underneath the cup.

    The magnets will all be carrying the same charge, so if a person happens to put their glass down on mismatched magnets, it should still work (Right? I think so). My question and problem is this:

    If the person set their cup down with the magnets touching 2 positive leads, what would happen? The whole thing will probably be running off 12v. I suppose this could be fixed with some spacing of the magnets and such, but if there's a way to make it not a problem, then I'd like to basically cover the entire table with them.

    My other problem is this: What about spills? Will a spill of water over the magnets, assuming a great seal between the glass and magnets, short out the system? I don't expect to be spilling, but I want to plan for the worst.

    Any suggestions for this project would be great, I just came up with it a few minutes ago.

    Thanks!
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    I don´t undersstand what are the magnets for?
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Magnets don't charge, are you talking electromagnets perhaps?

    Sounds like OP is talking about magnetic levitation.
     
  4. brianllama150

    Thread Starter Member

    Nov 6, 2008
    12
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    The magnets are connected to the LEDs that are connected to a battery. The cups will have a conductive bar or something on the bottom of them so that when they set on the magnets they complete the circuit. I was fairly confident that this would work, and people I've explained it to seem to think it'll work. Am I way off? Maybe I need a lesson in magnets then.

    please help,
    thanks!
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    The problem is the terms you're using. Electromagnets can turn on/off, but by far most magnets are permanent. You are talking like you are turning the magnets on and off (you don't "charge" a magnet, though you can charge a capacitor).

    Are these metal magnets, that you are using to conduct electricity to turn LEDs on/off? In this case the magnetic field has nothing to do with the electricity, they are coexisting side by side.

    If these are electromagnets then they will pull quite a bit of current, and will be very bulky indeed.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Perhaps instead you're thinking of using reed switches in the tabletop, and magnets on the bottom of the cups? Reed switches can be normally open, normally closed, or SPST with one terminal NO and another NC. They change states when a magnet gets near.

    However, that would just be an on-off type situation, which could get rather boring.

    Check out this instructible on an interactive LED table:
    http://www.instructables.com/id/Interactive-LED-table/
     
  7. HarveyH42

    Active Member

    Jul 22, 2007
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    I think he is trying to use the magnets as contacts of a switch.
     
  8. brianllama150

    Thread Starter Member

    Nov 6, 2008
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    Thanks everyone! You've all given me alot to think about and read, I will get back to you soon.
    EDIT: Those reed switches sound great! I don't know why I have never heard of those before, they sound PERFECT for that I'm looking to do. That interactive table you sent me was awesome, too, but a little too much for my abilities and budget.
     
    Last edited: Apr 14, 2009
  9. brianllama150

    Thread Starter Member

    Nov 6, 2008
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    0
    Well, this is what I was thinking would be really cool...cover the table with a 1:1 ratio of LEDs to reed relays. Anything else would be an engineering nightmare for me. Put the magnets on the bottom of the cups. That would look AWESOME. But then I realize that about 2000 leds and 2000 switches would cost be a lot.

    However, I think I'll just squeeze this idea smaller and make it into a beerpong table. Only apply it to the small triangular area underneath the cups. That would be pretty cool, too.

    The glass that I have access to, which is free, is 1/4 inch thick. How sensitive are typical reed switches/relays? Do the magnets have to be basically touching them or just close (1/4 inch away)?
     
    Last edited by a moderator: Apr 16, 2009
  10. Wendy

    Moderator

    Mar 24, 2008
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    Close is usual, depending on the magnets. Think alarm systems, magnets/reed switches are used for doors and windows.
     
  11. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    If cost is a factor, one might consider Hall effect sensors. Depending on where one buys one's parts, they might be less costly than the reed switches.
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    This is another nifty one, The Chessboard
     
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