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Stepper motor

Discussion in 'Sensors and Actuators' started by woodzer2, Apr 5, 2017.

  1. woodzer2

    woodzer2

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    Apr 5, 2017
    Hello all..
    I'm looking for suggestions for a project. I need to control a DC stepper motor, 3 separate speeds with a momentary switch for each speed. I hope to set up one revolution to a home position. The movement cycle would be the same for the stepper but need the 3 separate speeds with 3 separate switches. Any ideas?
    Thank you in advance.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    To operate the stepper you'll need a stepper controller. I doubt you'll find one mathcing exactly your specs. Therefore it is most likely you'll have to build your own from a microcontroller (e.g. arduino), a stepper driver (e.g. an arduino stepper motor shield) and 3 buttons or switches.
    Plus the necessary code to control the motor according to the buttons pressed.
    The programming is made easy by using a free stepper motor library.
     
  3. woodzer2

    woodzer2

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    Apr 5, 2017
    Thank you very much for the info, as I thought this may be too much for me to attempt.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Why do you think you need a stepper motor? What is your application?
    Stepper motors are typically used to turn the axle by precisely defined steps (hence the name ;))

    If you simply want the motor to turn to a home position, any DC motor will do this. Speed may be varied simply by using differnet voltages or, as mostly only one voltage is available, by using different resistors in series with the motor.
    Stop at the home postion can be achieved by a limit swithc that interupts power to the motor once home position is reached.
    An RC servo can be 'abused' by removing th electronics from the servo and providing power directly to the motor (via the switches and resstors, of course). This gives you an actuator attached to the motor axle which you can use to do useful wrk with the motor.
     
  5. woodzer2

    woodzer2

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    Apr 5, 2017
    if you could picture a small wave tank, the motor via linkage will actuate a paddle if you would, with three separate intensities. Hence the reason for the 3 separate momentary switches. The 1st switch would run the linkage through one cycle at a moderate level, the 2nd switch would be a faster cycle of the same and the 3rd switch would be the holy cow speed.
     
  6. woodzer2

    woodzer2

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    Apr 5, 2017
    oh and sorry, already have a DC position control motor on hand.
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    What do you think of this proposal:
    upload_2017-4-6_18-3-54.png
    V1 is your power source, the voltage set to the max. acceptable voltage for fast operation.
    Resistors R1 and R2 are set such that the motor operates at the expected medium or slow sped, respectively.
    The 3-way switch to the left selects either of the 3 possible speeds.

    To the right there is a switch (lower) and a pushbutton (upper).
    The switch is a limit switch which is open in the end position of the motor, closed while the motor is running (away from the end position).
    The pushbutton is a normally open type which will short circuit the limit switch when pushed.

    The operation is as follows (assuming the motor is at rest in the end position):
    1. Select the desired speed by setting the 3-way switch to low, medium or high.
    2. Start the motor by pushing the pushbutton until the the motor has left te end position.
    3. The motor having left the end position, the limit switch will now be closed. The motor will continue running.
    4. When the motor reaches the end position, the limit switch will open. As the pushbutton is no longer pressed (for one cycle operation), the motor will stop in the end position.
    If you need to run multiple cycles, simply keep the pushbutton pressed so the limit switch will not interrupt the power in the end position.
    You may have to tweak the mechanical setup such that the motor really stops in the end posistion even when set to high speed. Since the motor will not stop immediately when power is turned off, there is the risk of the mechanical inertia of the machine letting the motor run past the limit switch which in turn will re-close the limit switch and the motor will be powered again.
     
  8. woodzer2

    woodzer2

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    Apr 5, 2017
    I do thank you for this route to follow, however I'm afraid I can not remove the 3 separate momentary switches from the design. If that were possible then your design would solve the dilemma. Could I use line voltage to each switch R1 being full power to motor, R2 being a resistor and R3 a resistor. Any of the switches would energize the circuit pulling the motor off the end switch to run a cycle. It would have to be staged in such a way that only one cycle would run at a time?
    Thanks again for your time.
     
  9. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    If you dont want or can't se an electronic solution, here's a take at a comletely electromechanical solution:
    upload_2017-4-7_12-30-6.png
    You'll need 2 coil latching relays with 2 contacts.
    The setup works as follows:
    When a pushutton is pressed the associated relay is 'set', turning on the motor at the selected speed. At the same time the 'reset' path is interrupted to avoid a conflict between the set signal and the reset signal from the limit switch. You'll have to push the button as long as it takes for the motor to leave the end position and to release the limit switch. Otherwise (very short push), the limit switch will still be closed when you release the pushbutton and the circuit wil reset immediately.
    When the motor reaches the end position, the limit switch is closed, and resets the relay, thus turning off the motor.

    An electronic (solution really would be more elegant.
     
  10. woodzer2

    woodzer2

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    Apr 5, 2017
    If only I had the mental ability for the electronic solution.
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    I'm sorry, I currently do not have the time to work out one.

    Anyone else step in?
     
  12. woodzer2

    woodzer2

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    Apr 5, 2017
    you have already been a tremendous help.
     
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