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egg turner for an incubator

Discussion in 'Electronic Design' started by [email protected], Jun 9, 2007.

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  1. Guest

    Hi there,

    could someone with more of a brain than me help with a design for an
    egg turner? basically i need to somehow use an RS 343-997 multi
    function timmer that has an SPDT relay inside to control a motor that
    will rotate CW untill a limit switch is pressed, then wait an hour
    before rotating CCW untill another limit switch is pressed......wait
    an hour and so on.

    would it be possible? maybe with another SPDT relay wired parallel to
    give me the contacts needed for polarity reversal?

    i have to use this SPDT timer as i am on a very tight budget and have
    it to hand!

    This project is of a charitable nature for a kenyan village if i can
    get it sorted out.

    yours faithfully in advance,

  2. Bruce Varley

    Bruce Varley Guest

    Someone may come up with something smarter, but I think you'll need a
    bistable element as well as that timer, from a quick look at my ancient RS

    The bistable element could be a toggle relay, one that changes it's output
    contact state every time the input coil pulses on. I have a beautiful old
    Omron with a 24VAC coil sitting on the shelf, if it'll assist you're welcome
    to it for nix, just email. The local kids will watch it in fascination for

    Wired so that motor is deenergised when either of the limit switches is
    active, ie. the egg thing is at either extremity.

    Set your timer to generate regular short on pulses, say 10 seconds,
    separated by an hour (Asymmetric recycler mode if I read the book
    correctly). Use that pulse to pulse the toggle relay, to reverse the
    direction of the motor, and also to bypass the limit switch interlock. Thus
    for 10 seconds, the motor runs despite the limit switches, but in a
    direction that takes it away from the limit. By the time the pulse has
    finished, the limit switch is clear, so the motor will keep running until it
    hits the other switch, and stop.

    Just another thought, if this really is for a poor Kenyan village, then this
    RS component is a bit of an odd choice. Way over engineered for the task at
    hand, and undoubtedly not cheap. Also, being electronic, it may not
    appreciate the sort of power supply it may have to put up with. I'm sure
    someone here will come up with something better.

    remove ecks and kyoo to email.
  3. Tim Wescott

    Tim Wescott Guest

    A poor Kenyan comes to mind.

    Tim Wescott
    Control systems and communications consulting

    Need to learn how to apply control theory in your embedded system?
    "Applied Control Theory for Embedded Systems" by Tim Wescott
  4. Bruce Varley

    Bruce Varley Guest

    Better ... no bistable relay required. Latch a normal relay on one limit
    switch, delatch it on the other one. Use a contact from that relay to
    control the motor direction.
  5. Meat Plow

    Meat Plow Guest

    Or have a couple village kids rotate the eggs by hand like the Amish do.
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  6. Brian

    Brian Guest

    Eggs don't have to be turned back and forth. Rolling them works. Like
    in the old round metal Brower incubators. Can use a clock motor (hour

    Or, make some rollers the eggs rest on. Turn the rollors with a slow

    Most cheap incubators do rock the eggs back and forth, but use a
    unidirectional motor canged to bidirectional by the peg in groove
    mechanical part.

    Make sure your thermostat can sold within 1 F, thats way more
    important. After 7 days or so, turning isn't even necessary anymore.
  7. Wim Ton

    Wim Ton Guest

    diode endswitch
    ------->|----/ -----| DC motor
    AC-----/ |------O----- AC
    --------|<---/ ----- |
    diode endswitch
  8. A spatula?
    Simpler than that: Use a SPDT limit switch, arranged so that when the
    egg roller reaches one
    limit, it flips the switch to the opposite contact. When the motor
    turns the other way, the limit switch remains as is until it reaches the
    opposite limit, then flip back. Use the following circuit:

    Relay +---------------+---------------+ Limit switch
    | |
    | |
    CCW command o o CCW Limit
    \o--------- Motor ---------o\
    CW command o o CW Limit
    | |
    | |
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