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Latching relay? for 4way switch

Discussion in 'Electronic Basics' started by noel, Nov 11, 2003.

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  1. noel

    noel Guest

    Hello,
    Could someone explain how a latching relay operates. I understand the a DC
    type uses a positive pulse and a negitive pulse. I not sure how that would
    work or how the wiring would look. I would also like to know how an AC type
    would work. I assume that it works by applying current to the proper coil,
    or the proper end of it. Is there just a single coil in both types or what?
    Thanks
     
  2. Lord Garth

    Lord Garth Guest

    Sounds like you're describing a bistable relay. This type has 2 coils and
    when
    pulsed, the relay latches the appropriate contacts with no holding current.

    Are you asking for an X10 or computer controlled 4PDT relay? There are
    X10 SPDT relays made...use 4, all set to the same address.
     
  3. Anders

    Anders Guest

    There is 3 different ways to solve this.
    1. one coil that is polarized and that mechanicly flipps to each position
    2. two coils that mechanicly flipps to each position
    3. one coil that mecanicly is locked in each position like a pushbutton that
    stays in each position.
     
  4. There are several kinds. One kind has a magnet on the coil, so when
    the coil pulls in the armature, it stays pulled in. You have to
    reverse the polarity of the coil current to 'unpull' it. Another
    similar relay uses two coils, one to pull in and one to pull out.

    Another latching relay uses a mechanism similar to a ball point pen.
    Every time the coil pulls the solenoid in, it clicks a latch or
    rotates a cam. The second pull disconnects the contacts.

    I've seen a latching relay that's a sliding bar with a coil at each
    end. The bar shuttles back and forth, and the lobe or bump on the bar
    makes or breaks the contacts as it moves.

    And then there's a regular relay that's driven by a flip-flop that
    toggles on and off. And for DC, the SCR could make a solid state
    relay, but it would have to be commutated to turn it off.


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  5. Did everyone hear that X10 went bankrupt? The SOBs that annoyed us
    with pop-up and pop-under camera ads won't be bothering us anymore.
    Good riddance to bad rubbish!


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    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
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    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
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  6. And #4 - regular relay driven by a flip-flop.



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    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
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  7. Lord Garth

    Lord Garth Guest

    Interesting and goodbye! I don't think the X10 website was owned by the
    same company that invented the X10 carrier current system....I could be
    wrong though! I seem to remember the product originally had the BSR
    name.
     
  8. Yes, but they spun off the X10 line into a separate company. FYI,
    Leviton makes X10 compatible devices and many more that X10 doesn't
    make. Some are very interesting and all are expen$ive.
     
  9. #5 - A permanent magnet keeper. When the fields add it latches in.
    When they oppose it latches out. (The permag doesn't have enough
    strength to move the relay by itself, but enough to keep it.)

    #6 - One solenoid on a ratchet/cam. One pulse closes the contact, the
    next toggles it open. If on/off operation is desired, in each state
    sample to make sure it's in the desired state and energize again if not
    (e.g. X10 appliance modules).
     
  10. Fred Abse

    Fred Abse Guest

    And #5 - simplest of all, one contact of the relay used to hold the coil
    energized. used more than any other method, IME.
     
  11. Ross Mac

    Ross Mac Guest

    There is a way to make a normal relay latching by using one set of the
    contacts to create the latch. A momentary switch would pull the contactor in
    and the contacts would hold it in and another momentary switch would drop it
    out by opening the coil voltage. The momentaries can easily be replaced by
    other devices.........
     
  12. My understanding, as described to me by one of my former
    acquaintances who was an aircraft electrical systems guy at Boeing...

    What you refer to is also, sometimes, called a 'balanced force'
    relay, and they are frequently used in aircraft and military
    applications. They have two coils, and two small permanent magnets.

    When at rest, the relay's armature is held in said resting
    position by one of the permanent magnets. When current is applied to one
    of the coils, the pull is enough to overcome the opposite permanent
    magnet, and to bring the relay's armature to the opposite state.

    The permanent magnets help to insure that exactly the same force
    is applied to the relay armature no matter which coil is energized. They
    also serve to reduce or eliminate contact bounce, thus allowing the
    relay to operate reliably under high-vibration conditions.

    What you describe (a single coil using differing polarities for
    each direction) could probably be done (heck, already has been done I
    think) as well.


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  13. norm d.

    norm d. Guest

    Latching relays have 2 coils. You apply power to one and the contacts change
    like a latching switch. You don't have to maintain power to the coil for the
    contacts to maintain the new position. Apply momentary power to the 2nd coil
    to flip the contacts back to the initial condition.
     
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