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  • CAN or PWM?

    Hi everyone
    question.... What is the difference between CAN and PWM setup systems? Can someone explain what they are and which set up we should use?

  • #2
    Re: CAN or PWM?

    Lets start with the similarities, both of them allow for the control of the output voltage of a speed controller.

    The differences are listed below:
    * CAN is a serial bus, PWM requires a cable going from the DSC to each controller (Comparison diagrams can be found here: robotics.aca.imsa.edu/can)
    * CAN allows for feedback from the controller on its status, PWM is a one way communication
    * CAN allows for sensor processing directly on the Jaguar, PWM must be controlled from the cRIO
    * CAN allows for closed-loop control on the Jaguar rather than the cRIO
    These are just some examples of the differences, there are probably more I am forgetting.

    As for which one you should use, it depends a lot on what you plan to do and how much experience you have. If you just need to control motors and haven't had much experience in wiring FRC robots and building their control systems, then I would suggest using PWM. If you have time to experiment, wanting feedback from the controller, wanting to have closed-loop control moved to the motor controller, or are willing to learn more complex systems, then CAN is a good choice.
    Last edited by trekke20; 01-14-2011, 12:56 AM. Reason: Fixed spelling error
    -Ian McInerney
    Lead Programmer, Team 2022

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    • #3
      Re: CAN or PWM?

      The fundamental technical difference is that CAN is a packet-based protocol over a shared bus while PWM is just variable-length pulses being sent down the wire.
      textnav - 2 second downloads, comments that stay with code, no more broken wires and annoying NXT-G problems - http://code.google.com/p/textnav2/

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      • #4
        Re: CAN or PWM?

        Originally posted by trekke20 View Post
        Lets start with the similarities, both of them allow for the control of the output voltage of a speed controller.

        The differences are listed below:
        * CAN is a serial bus, PWM requires a cable going from the DSC to each controller (Comparison diagrams can be found here: robotics.aca.imsa.edu/can)
        * CAN allows for feedback from the controller on its status, PWM is a one way communication
        * CAN allows for sensor processing directly on the jaguar parts, PWM must be controlled from the cRIO
        * CAN allows for closed-loop control on the Jaguar rather than the cRIO
        These are just some examples of the differences, there are probably more I am forgetting.

        As for which one you should use, it depends a lot on what you plan to do and how much experience you have. If you just need to control motors and haven't had much experience in wiring FRC robots and building their control systems, then I would suggest using PWM. If you have time to experiment, wanting feedback from the controller, wanting to have closed-loop control moved to the motor controller, or are willing to learn more complex systems, then CAN is a good choice.
        I loaded a Black Jaguar with v89 then switched back to PWM later without any issues..
        Last edited by kurtdaniel; 10-22-2011, 03:54 AM.

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