Reversing polarity with 2 SPDT switches and 2 SPDT relays to control an actuator.

Discussion in 'The Projects Forum' started by eyeowah, Jun 19, 2016.

  1. eyeowah

    Thread Starter New Member

    Jun 6, 2016
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    0
    I'm trying to come up with a trolling motor steering control, left and right, using 2 SPDT switches and 2 SPDT relays. I'm using Bosch style relays where pins 85 & 86 are the coil and pin 30 is switch with 87a being nc and 87 no. I've tried applying knowledge from this thread: http://forum.allaboutcircuits.com/threads/using-2-spst-switches-to-control-a-linear-actuator.80630/ but have little experience with this type of wiring. I'm confused how to physically wire the circuit to get the expectant outcome. Any help is much appreciated.
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    Not being familar with a steering control, does the polarity to the motor determine which direction it turns? If so you can use one switch to turn on the system and the other switch to control the direction with the two relays reversing the polarity. If this sounds right let me know and I will
    draw you a diagram.
     
  3. eyeowah

    Thread Starter New Member

    Jun 6, 2016
    3
    0
    The 2 switches are foot pedals. I would like to press the left switch to extend the actuator and the right switch to retract. The actuator is a 12vdc and changes direction by reversing polarity. Doesn't require limit switches. Thanks for the help.
     
  4. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,138
    200
    EASY:

    The common side of the relays goes to one side of the motor respectively.
    The NC side of each relay goes to ground.

    The mental picture you should get here is, the motor is grounded on each end when the relays are off.

    The NO position of each relay goes to +12.

    Now, your mental picture should see that if one relay is activated the motor goes one way and if the other is activated it goes the other.
    When both or neither is activated nothing happens.

    Wiring the pedals to activate each relay should be the easy part.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,774
    1,103
    Putting KISS's description into picture form :-
    Reverser.PNG
    Note that a Bosch relay may include a diode across the relay coil, so polarity of the coil is important. The internet has conflicting views as to whether pin 85 or pin 86 should be grounded. Pin 86 should go to ground (as I show in the above pic) if the diode anode is connected to pin 86. Check the resistance between pins 85 and 86 to determine the diode polarity.
    If the diode anode is connected to pin 85 then the wiring would be like this :-
    Reverser2.PNG
    This item refers to the possible diode presence.
    If your actuator moves the wrong way when a pedal is pressed, just reverse the two connections to the actuator.
     
    Last edited: Jun 20, 2016
  6. eyeowah

    Thread Starter New Member

    Jun 6, 2016
    3
    0
    Thanks for the graphical representation. This circuit will be placed on a kayak and at times I'll be wearing heavy boots. What would happen if both switches were pressed at the same time? Wouldn't I be causing a short?
     
  7. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,138
    200
    from post #4:

     
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