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Re: Sealed magnetic reed switch

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  • Tom
    Good morning Richard, Thank you, thank you for all of the excellent info. I m excited to get going on this voyage, especially after your comments. I can see
    Message 1 of 6 , Jan 25, 2011
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      Good morning Richard,

      Thank you, thank you for all of the excellent info. I'm excited to get going on this voyage, especially after your comments. I can see now, that I will need to do some exploring with adjustable parts just as you did when you got into the magnetic/switching area. Thank goodness I saved many of your photos and explanations since it was reported that they were all lost during the switchover to this new group website.

      Yes, I intend to report my progress, but for now it will probably be all questions. :0)

      73
      Tom
      W4TMW



      "richard_meiss" <wb9lpu@...> wrote:
      >
      > Hi, Tom -
      >
      > Welcome to the world of magnets and reed switches. Good rare-earth
      > magnets are available from several places on the web. I am a customer
      > of K&J Magnetics (http://www.kjmagnetics.com
      > <http://www.kjmagnetics.com/> ) and Magcraft (http://www.magcraft.com
      > <http://www.kjmagnetics.com/> ). Both of these companies have proved to
      > be fast and reliable.
      > Satisfactory reed switches are a bit harder to find. I have
      > acquired a lot of them at hamfests - the ones that I find the most
      > useful are about 1/2" long and 3/32" in diameter. One place to find
      > them on the web, or by mail, is at All Electronics
      > (http://www.allelectronics.com/make-a-store/item/RSW-27/SMALL-REED-SWITC\
      > H-N.O.//1.html
      > <http://www.allelectronics.com/make-a-store/item/RSW-27/SMALL-REED-SWITC\
      > H-N.O.//1.html> ). Their stock varies from time to time, so I get a
      > bunch of them when they are available. Some places sell them for use in
      > alarm systems, but these types tend to be pretty large.
      > There are a few things to keep in mind when working with the
      > glass-encapsulated reed switches. They are fragile, so I mount mine in
      > brass tubes (5/32" diameter) for protection. This size of tube will
      > accept the switch and allow for passage of connecting wires. The
      > switches are surprisingly tolerant of soldering to the leads, as long as
      > you are quick, but bending the leads (especially near to the switch
      > body) is asking for trouble.
      > Some other things to be aware of. Magnetic reed switches show
      > hysteresis - that is, the point in a magnetic field where they turn on
      > is different from where they turn off (they become slightly magnetized
      > themselves). This is great for use in bugs, where there is a fair
      > amount of pendulum movement - the hysteresis completely eliminates the
      > "scratchy dits" problem. But in a straight key or paddle, this can pose
      > a little problem. If you have a magnet on the key lever, as you push
      > the key down the switch will close at some point (which you can set to
      > be the end of the stroke). But as the key lever moves back up, the
      > switch will stay closed for a small space. This means that you might
      > not be able to set the travel distance to be as small as you would want
      > - especially in a paddle.
      > The switches also have "hot spots" that you can map by moving a
      > small magnet around them. The sensitivity falls off with distance
      > differently depending on the hot spot chosen. I have also found that
      > the switches work predictably as long as the current switched is quite
      > low (as it is with a modern keying circuit). If you try to switch a
      > higher current, the flowing current changes the characteristics of the
      > switch in a rather unpredictable way. So if you are trying to key a
      > "boat anchor", a keying relay is in order.
      > Most of these properties can be turned to your advantage with
      > careful design. Best of luck with your experiments, and let us know
      > what develops.
      >
      > 73 de Rich, WB9LPU
    • k5est
      Wow, well done and great info, Rich! Many thanks for the tutorial that saves a lot of experimenting and crazy head scratching!!! 73....Walter - K5EST ...
      Message 2 of 6 , Jan 25, 2011
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        Wow, well done and great info, Rich!
        Many thanks for the tutorial that saves a lot of experimenting
        and crazy head scratching!!!
        73....Walter - K5EST


        --- In cw_bugs@yahoogroups.com, "richard_meiss" <wb9lpu@...> wrote:
        >
        > Hi, Tom -
        >
        > Welcome to the world of magnets and reed switches. Good rare-earth
        > magnets are available from several places on the web. I am a customer
        .............snip..........
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