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PWM that will work with a reversible power supply

Discussion in 'Power Electronics' started by Bobwhite, Jan 28, 2021.

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  1. Bobwhite

    Bobwhite

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    0
    Jan 28, 2021
    I am running a small 12 volt motor with a 12 volt, reversible, remote controlled power supply. I need to be able to adjust the speed of the motor. I have seen PWMs with a reversible switch, but that would not work for my application. Is there an off the shelf PWM that will work with reversible current ? All the ones I've seen say reversing the polarity will damage the PWM.
     
  2. Bluejets

    Bluejets

    5,167
    1,081
    Oct 5, 2014
    No.
    Pwm control will need to be before reversing switch.
     
  3. Bobwhite

    Bobwhite

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    0
    Jan 28, 2021
    Thanks
     
  4. Bobwhite

    Bobwhite

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    0
    Jan 28, 2021
    Couldn't you put a potentiometer in the circuit to slow the motor speed? What would happen when the poles were reversed to the POT?
     
  5. Bluejets

    Bluejets

    5,167
    1,081
    Oct 5, 2014
    Pots are normally rated at around 1/4w, not suitable, and resistance inclusion also defeats the purpose of using pwm.
     
  6. bertus

    bertus Moderator

    2,164
    811
    Nov 8, 2019
    Hello,

    Could you use a DC control voltage?
    Then have a look at the attached article.
    The control voltage can be in place of the potmeter.

    Bidir_speed_control_schematic.png
    At ca. 52 % Vcc the speed is max forward.
    At ca. 33 % Vcc the speed is 0.
    At ca. 5 % of Vcc the speed is max reverse.

    Bertus
     

    Attached Files:

  7. Bobwhite

    Bobwhite

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    0
    Jan 28, 2021
    Can I add the PWM before the power supply? Will the PWM effect the operation of the reversible, remote controlled power supply?
     
  8. bertus

    bertus Moderator

    2,164
    811
    Nov 8, 2019
    Hello,

    In the given circuit IC1b, IC1c and IC1d will perform the PWM action.
    It is controlled by the voltage coming from IC1a.

    Bertus
     
  9. Bobwhite

    Bobwhite

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    0
    Jan 28, 2021
     
  10. bertus

    bertus Moderator

    2,164
    811
    Nov 8, 2019
    Hello,

    No, you can not apply PWM on the powersupply.

    Bertus
     
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