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NOT/OR gate for 9 volt

Discussion in 'Electronic Basics' started by mail4happy, Feb 5, 2004.

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  1. mail4happy

    mail4happy Guest

    I have a gate that cost me an arm and a leg. I don't want the daughters
    backing into it as they try to navigate out the driveway. I want to have a
    horn go off if the gate is not fully closed or not fully opened. A 9 volt
    battery would run the buzzer/horn while the gate is in the transition state
    of closing/opening. The only way I can figure to wire this up is:
    IF [Not (closed)] OR [NOT (opened)} THEN Horn
    ELSE no horn

    or maybe

    If [Closed] OR [Opened] Then No Horn
    ELSE NOT [output-> circuit to
    horn]

    This would allow me to have two contact closures, one at each end of sliding
    gate...BUT it also require both NOT gates and OR gates....!

    How is this done?

    Thanks in advance

    Tom Johnson
    Baldwin Park, California
     
  2. Hi Tom:

    You're making this way harder than it needs to be. All you need is two
    normally-closed switches: one that breaks when the gate is open and one that
    breaks when the gate is closed. Wire them in series between the positive
    side of the battery and the horn. Wire the negative side of the battery
    directly to the horn.

    When the gate is open or closed, one of the switches will break the circuit
    and the horn will not sound. If the gate leaves either switch, it will
    close and turn the horn on until either switch breaks the circuit again.
    With a circuit like this you could even use a 120 Vac whoop-siren! That
    ought to get their attention!
     
  3. Michael

    Michael Guest

    Use two normally closed contacts in series with the buzzer (like the
    light switches in a fridge), so that when the gate presses them at
    either end it opens the circuit and stops the buzzer.

    If you wanted to improve on that, you could put a beam accross the
    driveway so the buzzer only sounds if they approach the gate.
     
  4. Robert

    Robert Guest

    I am guessing this is what you require,

    Horn will only go off when gate is either not closed or not open. So
    when ever it is closed or open it wont horn right?

    all that is required then is just a single NOR gate, one input
    indicating Closed and one indicating Open, don't know how you will
    implement those signals but that is all you require.

    Hope that helps

    Rob
     
  5. John Fields

    John Fields Guest

    ---
    Or an OR or an AND or a NAND or two mechanical switches wired in
    series, which is the RIGHT way to do it as you might have found out if
    you'd have taken the time to READ THE FUCKING THREAD.

    You're guessing that what's running around in that peabrain of yours
    is what he needs, and you don't have a clue as to how he's going to
    hook it up to make it work, but for some reason you felt compelled to
    grace the group with your profound insight.

    Why????
     

  6. Boys....where's the love?

    Don
     
  7. Steve

    Steve Guest

    Forget the logic gates. I would go with "normally closed" reed
    switches, and a strong magnet attached to the gate in an appropriate
    place. Or perhaps you'll need two magnets; hard to say without seeing
    the gate in situ!

    (Actually, which state is "normal" for a reed switch. Does normally
    closed mean that it's closed when it's NOT affected by a magnet? Or
    is the other way around?! Seems like a vague description to me.)

    Have the 9V wired through one switch, then the other, then to the
    buzzer/horn.

    Gate fully closed, magnet opens one switch, no current.

    Gate opening, both switches closed, BZZZZZ!

    Gate fully open, magnet opens other switch, no current.

    Is this an electric gate? Perhaps you just need to tap into the
    voltage supply to the open/close motor!? Probably works on the same
    principal as what I've described.

    niftydog
     
  8. John Fields

    John Fields Guest

    ---
    Probably 99% of the reed switches manufactured are what is known as
    "Form A" which means that the contacts are normally open when not in the
    presence of a magnetic field. This presents a problem in that the
    switches want to be closed _except_ when the gate is fully open or fully
    closed. Not an intractable problem, however, but rather one that can be
    easily solved with the use of bias magnets. What is done is that the
    bias magnets are located near each switch (to hold the switches closed),
    and the gate carries another magnet which, when it approaches either
    switch, cancels the field of the bias magnet. This forces one switch to
    open when the gate is fully open and the other to open when the gate is
    fully closed. Reed switches are also a good idea because they're
    impervious to the weather and this sounds like an outdoor application.
     
  9. JeffM

    JeffM Guest

    I want to have a horn go off
    |
    +--------+
    | ___|__
    / | | /
    \ |BUZZER| /
    / |______|/
    \ |
    | |/
    +--+------|
    | |
    \ |>
    \ |
    o |
    | |
    \ |
    \ |
    o |
    | |
    +-----------+
    N.C. __|__
    REED SWITCHES ___
    (MAGNETS ON _
    DETENTS)
     
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