Reversing Polarity With SPDT Relays

Discussion in 'General Electronics Chat' started by race-team420, Nov 25, 2009.

  1. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    I am trying to reverse polarity for a 12V actuator by using SPDT relays. Is it possible to operate the actuator in both directions by using a SPST switch???
    Thanks!
    Jeff
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can if you use two SPDT relays.

    Connect A+ to relay1 Common and A- to relay2 Common.
    Connect V+ to relay1 Normally Closed and to relay2 Normally Open.
    Connect V- to relay1 Normally Open and to relay2 Normally Closed.

    When the relays are energized the voltage across the actuator will reverse. If you want to stop the actuator completely then you have to use another relay3 between the battery and relay1 (SPST is fine) with its Common connected to V+ and its Normally Open to relay1 Common. To energize the actuator you will need to energize relay3. To control the voltage polarity across the actuator use relay1 and relay2 (both energized the same time).

    V+=power supply positive
    V-=power supply negative
    A+=actuator positive
    A-=actuator negative
     
  3. Jumper

    New Member

    Nov 25, 2009
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    I controlled the direction of a 12v actuator by using a DPDT center-off switch. I don't know how the forumn posts electrical schematics or I would draw it out for you, assuming you can use a DPDT switch instead of a relay.
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    Maybe he wants to control this by a means of control circuit and not by hand but he can still use a DPDT relay instead of two SPDT relays.
    To post a circuit you can convert it to PDF or take a snapshot of it and attache it here (there is an attachment clip above). I don't suggest you to just save it and post the file because the OP, who wants to see it, may not have the same design software as you.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here's a version with limit switches:

    [​IMG]

    The direction switch S3 shouldn't be suddenly reversed; it's hard on the actuator.

    If you want to stop or reverse along the way, you should have a center off type switch.

    The advantage of using two SPDT relays is that you get braking action when both relay coils are de-energized. This stops the actuator much more quickly than if it is allowed to "coast" down.
     
  6. Jumper

    New Member

    Nov 25, 2009
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    Thanks. I'm new here :rolleyes:
     
  7. mik3

    Senior Member

    Feb 4, 2008
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    Welcome to the forum then :p

    For example, see how SGtWookie posted his circuit.
     
  8. race-team420

    Thread Starter New Member

    Nov 25, 2009
    9
    0
    I must use a spst switch i know it would be much easier using a dpdt or even a spdt switch. Would I still need to use a 3rd relay even if i am going to use a limit switch to stop the actuator?
     
  9. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    If the limit switch can handle the current of the actuator and the circuit voltages then you can use it in the place of relay3.

    What is the application?
     
  10. race-team420

    Thread Starter New Member

    Nov 25, 2009
    9
    0
    I am making a tilting pump for a jet ski that tilts vertically. I just have an actuator that is used to tilt the jet now i just need to fiqure the electrcial part out... sorry MIK3 what do you mean by relay 1 or 2 common??
     
  11. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    If you look at SGts diagram, it is the relay contact in the center (where the motor is connected on).
     
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