MOTOR CONTROLLER CIRCUIT

Discussion in 'The Projects Forum' started by superna, Feb 6, 2015.

  1. superna

    Thread Starter New Member

    Feb 6, 2015
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    HI,
    I am working on a project which utilizes a 12v dc geared motor, connected to a acme screw, moving an object up and down.(Travel is only 4 inches).Object load will be 1 Kg Max.
    The input will be 12v battery.
    The Driver for the motor has a input for reversing the direction(requires a high on the input to do so)
    http://www.robokits.co.in/documentation/DC_Motor_Driver_24V_20A.pdf
    I will be installing two Limit Switches (one at the top and one at the bottom) to limit the travel.
    The object after starting from the bottom will travel to the top and needs to stay there. (motor supply cut off)
    The object after starting from the top will travel to the bottom and needs to stay there. (motor supply cut off)
    The initial command for the motor to run will through a on- off switch(later through a pc, not sure)
    could you guys please assist me with a circuit to do this.
    superna
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Welcome to the forum.
    It is do-able with that controller and the limit switch method is simple enough.
    Do you have SPST or SPDT limit switches.
    A picture and no. of the switch you have or planning to install will help to speed up things here. We need that info to throw a circuit for you.
     
  3. superna

    Thread Starter New Member

    Feb 6, 2015
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    The limit switch is planned and not purchased yet.
    So depending on the circuit requirement, it will be procured.
    superna
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I read the data sheet for the motor driver. To utilize it to run the motor as you describe requires a double-pole, double throw toggle switch (for starting and reversing), and two normally-closed switches (up limit and down limit).

    Do you have any info on how much current the motor draws during starting? while running? Can you measure the unloaded running current with your multimeter in the 10A range?

    The reason I ask is because you don't need to use that motor driver. The only thing it brings is that the switches described above do not need to carry the motor current; only a few mA for the logic inputs. The difference in price between a 1A and a 10A switch is not enough to buy the kit. A DPDT toggle switch and two NC limit switches can control the motor directly, without the driver, as long as the switch contacts are rated for the motor current.

    Here is how to wire it without using the motor controller.

    142.gif
     
    Last edited: Feb 6, 2015
  5. superna

    Thread Starter New Member

    Feb 6, 2015
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    Hi Mike,
    The Driver board i already have it. So planning to utilize it.
    Also reversing the motor direction would become easy through the direction control input
    the Motor Details are:
    • 200RPM 12V DC motors with Metal Gearbox and Metal Gears
    • 32kgcm torque
    • No-load current = 800 mA, Load current = upto 7.5 A(Max)
      So basically i need to cut the motor supply at the end of the travel and then switch the direction using the driver board.
      If i need to get the signal to start the motor initially through a PC, then i think i need the Driver board.
      correct me if i am wrong
      Superna
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Try this. You will have to possibly reverse the motor leads so that the motor initially runs in the correct direction. R1 may not be needed if there is a pull-down inside the driver kit.

    142m.gif
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you use limit switches in series with a diode rectifier across each N.C. switch each rectifier fwd biased for the reverse direction, you just need to reverse the power to the series string, it save an extra conductor out on the actuator.
    Max.
     
  8. superna

    Thread Starter New Member

    Feb 6, 2015
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    Thank you friends for your support will try out and update.
    Superna
     
  9. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Here is a version which uses a SPDT direction toggle switch.

    142n.gif
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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  11. superna

    Thread Starter New Member

    Feb 6, 2015
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    Thanks Mike,
    Can you please give a small explanation on the circuit working with SPDT switch, so i can understand it better.
    Also If i need to eliminate the Spdt switch (which has to be operated manually)and get a signal from the PC, can this ckt be used.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The manual states that a 20hz to 400hz PWM signal is required for speed control, (PWM pin).
    Max.
     
  13. MikeML

    AAC Fanatic!

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    But isn't the pwm input the same as an enable input would be? I would read the manual thusly: "If you are going to use PWM, make the frequency no less than 20Hz. However even if the frequency is 20Hz, what happens if the duty cycle is 100%? Isn't that the same as using the pwm pin as an enable?

    btw- that manual is so bad, I wouldn't buy anything from robokits.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    PWM is quite different from active high/low signal, the board does not appear to have any modulation circuit itself for rpm control , so I assume the external is required from either a simple 555 circuit, or from a Micro-generated type.
    It is possible that taking the PWM to a high would be equivalent to max rpm and turn the outputs full on, if that is what is needed, it would have to be tried.
    The suggested frequency of the PWM signal, if used should be 20hz - 400hz.
    The OP did not appear to indicate whether or not he needs speed control?
    Max.
     
  15. Reloadron

    Active Member

    Jan 15, 2015
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    The manual could have been a little more specific. On many of these units placing a logic high on the PWM acts as an enable and a logic low as a disable in addition to normal PWM. I believe that is how Mike looked at it. The manual says:
    They also do mention the BRK so would Brake disable the output? That was my original guess till I started thinking about the PWM being held logic high or low.

    Meanwhile had a brief conversation with my wife before posting and see you guys are into covering it. :)

    This I can agree with:

    "btw- that manual is so bad, I wouldn't buy anything from robokits".


    Ron
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    According to the manual it says Brake ' brings immediate halt to the motor shaft' so I assume it uses dynamic braking?
    Max.
     
  17. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    It likely turns on both bottom devices (NFETs?) at the same time.
     
  18. superna

    Thread Starter New Member

    Feb 6, 2015
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    hi guys,
    I think the circuit with single SPDT switch is suitable.
    I don't require any speed control,and the motor i am using is a geared one with 200 rpm which is sufficient.
    Also i will not require any braking, as the stopping of the motor will be determined by the limit switches.
    one clarification is required regarding the circuit.
    switch position is DOWN, Limit position in NO, PWM input is put ground, DIR is also put to ground and
    switch position is UP, Limit position in NO, PWM input is put ground, DIR is also put to ground,
    what will be the status of the motor, will it be stopped or running.
     
  19. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The motor is stopped whenever PWM is low, regardless of what DIR is doing.

    If you ever convert it to computer control, use two bits and some diodes: one to control UP (in-series with the NC Up limit switch), and the other to control DOWN (in-series with the NC Down limit switch). The diode isolates the DIR input so that it is high only when running UP.
     
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