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Does PWM has current limitation?

Anonymous
Anonymous

Hello,

What is the safe way of using PWM in driving stepper motors?

Can we directly connect PWM pins to wires on the stepper motor? In this case, voltage difference between PWM pins will directly be applied to wire ends of the stepper motor, hence the current flowing throught the motor will also flow through the internal of the chip, entering at one PWM and comes out from another. If the current is large, is it possible for the chip to get burned?

If this is a limitation on the amplitude of the current, does this mean that we can only use PWM to motors with very small power (hence current)? Then are PWMs still good for any practical use?

Could anyone explain these to me?



Garry

  • 0
    TI__Mastermind 43875 points

    Garry,

    These PWM output signals are only control signals and cannot be directly connected to the motors.

    You must interface the control signals to your motors through power transistors. You should be able to find lots of examples on the internet for various motor interfaces.

    The output drive capability of the PWM output signals is in the mA range. The current requirements for motors will range from 100s mA up to many Amps and will be entirely motor dependent.

    BR,

    Steve

  • Anonymous
    0 Anonymous in reply to Steve Clynes

    Steve,

    Could you give some links/examples on how to build such a stepper motor controller completely from scratch, and that the resulted controller can be controlled by PWM?

     

    Garry

  • 0 in reply to Anonymous
    TI__Mastermind 43875 points

    Gary,

    I would first suggest that you do some research via Google etc... since this really depends very much on the types of motors you want to control.

    I am not a motor expert, so can't really add much more unfortunately.

    BR,

    Steve

  • Anonymous
    0 Anonymous in reply to Steve Clynes

    Steve,

    On which forum can I find experts on motor control?

     

    Garry

  • 0 in reply to Anonymous
    TI__Mastermind 43875 points

    I would start here...

    http://e2e.ti.com/search/SearchResults.aspx?q=motor

    BR,

    Steve

  • Anonymous
    0 Anonymous in reply to Steve Clynes

    Dear Steve,

    It seems that PWMs can completely be replaced by other means, and they are not necessarily needed at all in order to control stepper motors. Could you have a look at this post? I used the transistor idea that you told me just now, but there are a variety of ways to control them, why must be PWM?

     

    Garry

  • 0 in reply to Anonymous
    TI__Mastermind 43875 points

    Gary,

    First, PWMs are used for a LOT more things than simply stepper motor control.

    Likewise, there are many ways to control motors, PWM is just one.

    Now, I don't know much more about motor controllers, but I usually think about motor speed/power control when I think PWM and not particularly stepper motors.

    In fact, stepper motors inherently do not need PWM. Someone more knowledgeable on motors would need to comment more, sorry.

    BR,

    Steve

  • Anonymous
    0 Anonymous in reply to Steve Clynes

    Dear Steve,

    Thanks for the answer. I do with to hear more comments on this.

     

    Garry