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Help choosing a stepper driver

Discussion in 'Electronic Design' started by webzila, Oct 21, 2004.

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  1. webzila

    webzila Guest

    My group and I are working on a project where we plan to operate a door
    (open/close it) with the following voice recognition system & relay:

    Obviously we will need either a stepper motor or a dc motor to actually
    open/close the door. We looked at some stepper motor kits but most are
    operated by dip switches or jumpers but the whole point of our project
    is hands free operations.

    The voice recognition system has 10 relays (1 for each word that it is
    set to recognize). Can someone recommend a good/cheap stepper motor
    driver circuit or an IC that will be able to interface with the relay
    that I posted above and open/close the door at a specified speed.
    Any input/help would be appreciated.
  2. Rich Grise

    Rich Grise Guest

    It looks like you have on/off control. You don't need a stepper or
    any kind of controller. Well, depending what your outputs look like.
    If you have, say, a pulse, then use two relays - one for "open" and
    one for "close", and cross-couple them so it's bistable, and put
    limit switches at the ends of travel. Then just use any old motor
    and gear/belt/cog arrangement moves the door right. :)

    Any old _reversible_ motor. ;-)

  3. Steve

    Steve Guest

    Thanks for your reply.
    So you are saying that if I use a reversible motor then I wouldnt need
    a driver?

    I have to check on what kind of output the relay produces. From what I
    can see each numbered relay has a single-pole double-throw (SPDT)
    switch rated at 125 VAC at 0.5 amps or 24 VDC at 1.0 amps.

    Here is a pic of the relay (dont know if this shows or tells you

    So with this type of relay you are saying thats its possible to use a
    reversible motor instead of a stepper? How would the speed of this
    motor be controlled? Also, how would you control when the motor should
    stop turning (when the door is fully opened/closed).

    Thank you
  4. That's the interface board - no relays on it! The relay kit is shown
    to the right as 'SRI-02' in the diagram you linked earlier:

    (BTW, it seems to me those pages sometimes carelessly swap 'SR' with
    Yes. Where did the ideas of a stepper motor arise?
    Ambiguous question. Do you mean you want to vary the speed *during*
    each opening/closing? (Maybe to sort of tease the door user?) Or are
    you asking how to set a fixed speed for some motor(s) which you've
    presumably not tried and haven't described so far?
    As Rich said, use switches to detect the extreme positions. A variety
    of circuits are possible, depending on the detailed requirement. An
    alternative would be detecting increased current when the motor tries
    to take a leg off.

    Here's one I used for a Window Opener I made many years ago, using a
    surplus 12V windscreen wiper motor:

    A pair of N/C microswitches (SW1 and SW2) were carefully placed at the
    two extreme positions so that they are respectively opened when the
    window reached the fully open or closed positions. A SPDT switch (on
    left of first diagram), controlled whether I wanted to open or close
    it, and also BTW gave visual indication of the current state.


    Another approach which I've used recently for my Curtain Controller is
    shown here, and uses a bistable approach to control a screwdriver

    Note that this one uses two N/O (not N/C) microswitches. And *two*
    relays, one for power (on/off), and the other for direction
    (forward/reverse). Various N/O push buttons allow either open, close
    or (simpler) toggling, from either my wife's side of the bed or mine.
    An external dawn/dusk circuit (not shown) allows operation via the
    'Ext' inputs.

    I haven't got around to detailed notes on this yet. (IOW, the sort of
    notes I'll need 5 years from now to understand what the heck I was
    trying to do!) But - with some assumptions about your group's skill
    level - the relay/motor approach should be possible to understand from
    these two schematics.
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