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help with simple interface circuit

Discussion in 'Electronic Basics' started by [email protected], Mar 28, 2007.

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  1. Guest

    I have the following scenario. I have to do an automated blinds
    installation. The control circuit for the blinds consists of the
    following: A microcontroller which switches on two relays for up and
    down, a single motor does the up and down. Two limit switches input to
    the micro to prevent the rail from moving too far. The actual control
    consist of 3 buttons. Which supplies three 12vdc signals back to the
    microcontroller. Up, Down and Stop.

    The problem I am having is that I need to integrate this into my
    homeautomation device. It is a dynalite relay module. From which I
    normally use two relays. One for up and one for down. Usually the
    blinds I use only has neutral, a live for up and a live for down. So
    the cabling have been done already. I've only got 3 wires running to
    the blinds and I need to make this control circuit run with this.

    Any suggestions for a circuit?

    I've been thinking of using a relay which is wired common to 12V
    normally closed to stop and normally open to up and then another relay
    (or a double pole) with the common to 12V, normally closed to stop and
    normally open to down.

    The only problem I can see is that the stop signal will be sent to the
    micro the whole time.

    Otherwise I am going to have to reprogram the micro. It is an MDT and
    I don't carry any knowledge that type.

    Thank you

  2. Rich Grise

    Rich Grise Guest

    Assuming all of your signals are active high:

    From new ctlr To micro

    Up -------+-------------------- Up
    | _______
    +----\ \
    | NOR >o----- Stop
    Down ------+------------------- Down

  3. Guess that micro has nothing else to do but polling that UP/DOWN/STOP
    switches. So if it sees "STOP" most of the time, who cares? The micro will
    check whether the motor has been stopped and continue its polling. It will
    not get tired or complain.

    If you realy want to simulate the original buttons, you can do so using a
    spdt and a dpdt relais. See below. Named them X and Y respectively. (Only
    the contacts drawn, use fixed font.)

    \ x
    o \o
    | |
    +-------+ |
    | |
    | +-+
    | |
    | |
    o o
    \ y1 \ y2
    \ \
    o \o o \o
    | | | |
    | | |
    | | |
    | | |
    | | |
    Stop Down Up

    created by Andy´s ASCII-Circuit v1.24.140803 Beta

    petrus bitbyter
  4. ehsjr

    ehsjr Guest

    You have 3 wires to the blind operating motor.
    Go simple. Lose the ucontroller, use the limit switches to
    stop the motor, and do this:

    +12 -------+-------------------------+
    | |
    +---o o---+
    RY1-1 o---[Motor]---o RY1-2
    +---o o---+
    | |
    Gnd -------+-------------------------+
    Dynalite +12 --------[RY1]-----------+

    When your automation controller tells the blinds to open, the
    dynalite relay will energize RY1, which is installed at the
    blinds motor location, and the blinds will open. The limit switch
    will stop the motor.
    When the automation controller tells the blinds to close, the
    dynalite will drop the +12 on the line, so RY1 will drop and the
    blinds will close. The other limit switch will stop the motor.

    If the ucontroller is physically located at the motor
    location, you already have power there. If the power
    is there and you have thre additional wires for control,
    just ignore the stop line, and run the dynalite signal
    to a relay. Use the N/O & N/C points of the relay for
    close and open. Again, the limit switchs stop the motor.

    If you really want to complicate your life, use your automation
    controller to select several different relays, each of which
    selects a different tap on a voltage divider, and send that
    voltage on one wire to the blinds assembly. Detect the voltage
    and use it to determine how far to open the blinds.

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