Results 1 to 8 of 8

Thread: RS485 logic level in Dynamixel servos

  1. RS485 logic level in Dynamixel servos

    Hi all,

    I would like to know what the logic level (voltage) the RS485 transceiver on Dynamixel servos uses.
    Seems like this is not mentioned anywhere in Dynamixel's literature.

    Thank you.

    Regards,
    David

  2. #2

    Re: RS485 logic level in Dynamixel servos

    Are you talking about the voltage on the RS485 bus itself?
    That's covered by the specification for RS485.
    Or are you talking about the host side, where the MCU talks to the transciever?
    The modern Dynamixels use a STM microcontroller with 3.3V logic.

  3. Re: RS485 logic level in Dynamixel servos

    Quote Originally Posted by jwatte View Post
    Are you talking about the voltage on the RS485 bus itself?
    That's covered by the specification for RS485.
    Or are you talking about the host side, where the MCU talks to the transciever?
    The modern Dynamixels use a STM microcontroller with 3.3V logic.
    Yes the voltage on the RS485 bus itself.
    Ok, I assume that means I can use any voltage up to 5V, right?
    Thanks!

  4. Re: RS485 logic level in Dynamixel servos

    Quote Originally Posted by jwatte View Post
    Are you talking about the voltage on the RS485 bus itself?
    That's covered by the specification for RS485.
    That was what I was asking about. Good to know, thank you.


    Quote Originally Posted by jwatte View Post
    Or are you talking about the host side, where the MCU talks to the transciever?
    The modern Dynamixels use a STM microcontroller with 3.3V logic.
    I am also interested to know about the allowable voltage of VDC on the RS485 connector.
    Does this power the STM32 or only the RS485 transceiver?
    Would you know the maximum current draw on this supply per servo?

    Thanks again.

  5. #5

    Re: RS485 logic level in Dynamixel servos

    Sorry, I am not sure what you are asking. Although I must admit I have not used any of their RS485 version servos. All of mine are TTL level. Also not sure if anyone can answer some of these questions without knowing additional information like, which servo?

    For technical issues like internals of their servos, I would suggest that you contact Robotis directly, like their forum:
    http://en.robotis.com/service/forum.php

    Likewise I assume you might have looked at their Electronic Manual, to see what information that they may have already disclosed. Like for example for the MX64... https://emanual.robotis.com/docs/en/...specifications
    Again this was MX64, but you can then go to top level menus and get to any other servo.

    Good luck

  6. #6

    Re: RS485 logic level in Dynamixel servos

    For the Dynamixel servos (not Dynamixel Pro) the connector is rated at 3A continuous duty.
    The wires that come from Robotis are 22 gauge.
    This is slightly under-dimensioned for the heaviest duty you can get out of a strand of three servos, but it works OK in practice.
    The voltage for the servos is specified per servo; the AX series has slightly different acceptable voltage from the MX series has slightly different acceptable voltage from the XM series.
    Generally, the AX ones want "around 11V" with some variation, and the MX and XM ones want "a little over 12V" with some variation.
    I've run AX ones with 3S LiPo, and MX ones with 4S LiPo, as well as 4S LiFePO4 (the latter is actually ideal.)
    Note that the MX servos will detect overvolt over 16V input, so you have to make your 4S LiPo not be fully top charged if that's what you use. Also, the higher the voltage, the greater the risk that you overload the servo, overheat it, and ruin the motor. 12V is safer.

  7. Re: RS485 logic level in Dynamixel servos

    Quote Originally Posted by jwatte View Post
    For the Dynamixel servos (not Dynamixel Pro) the connector is rated at 3A continuous duty.
    The wires that come from Robotis are 22 gauge.
    This is slightly under-dimensioned for the heaviest duty you can get out of a strand of three servos, but it works OK in practice.
    The voltage for the servos is specified per servo; the AX series has slightly different acceptable voltage from the MX series has slightly different acceptable voltage from the XM series.
    Generally, the AX ones want "around 11V" with some variation, and the MX and XM ones want "a little over 12V" with some variation.
    I've run AX ones with 3S LiPo, and MX ones with 4S LiPo, as well as 4S LiFePO4 (the latter is actually ideal.)
    Note that the MX servos will detect overvolt over 16V input, so you have to make your 4S LiPo not be fully top charged if that's what you use. Also, the higher the voltage, the greater the risk that you overload the servo, overheat it, and ruin the motor. 12V is safer.
    Thanks again for your thorough reply jwatte.

    I'm a complete beginner to Dynamixel servos, and didn't realise that only the Pro servos have a separate power connector.
    So from your reply I understand that AX/MX/XM series servos expect a VDC of around 12V, which powers the entire servo (motor + controller).
    Thanks for this info. It's very helpful.
    Regards,
    David

  8. Re: RS485 logic level in Dynamixel servos

    Quote Originally Posted by KurtEck View Post
    Sorry, I am not sure what you are asking. Although I must admit I have not used any of their RS485 version servos. All of mine are TTL level. Also not sure if anyone can answer some of these questions without knowing additional information like, which servo?

    For technical issues like internals of their servos, I would suggest that you contact Robotis directly, like their forum:
    http://en.robotis.com/service/forum.php

    Likewise I assume you might have looked at their Electronic Manual, to see what information that they may have already disclosed. Like for example for the MX64... https://emanual.robotis.com/docs/en/...specifications
    Again this was MX64, but you can then go to top level menus and get to any other servo.

    Good luck
    Thanks for your help Kurt.

    I will check out the official Dynamixel forums and the Electronic Manuals.

    Cheers,
    David

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Question(s) Control Dynamixel MX28R via rs485
    By tony0 in forum DYNAMIXEL & Robot Actuators
    Replies: 0
    Last Post: 07-11-2016, 04:01 AM
  2. Interesting Rs485 halfduplex for Dynamixel with Teensy 3.1 without external Buffer chip
    By Elmue in forum Software and Programming
    Replies: 14
    Last Post: 03-14-2016, 03:52 PM
  3. Just For Fun Arduino Dynamixel RS485 using Max485 module
    By Jim Cheong in forum Arbotix, Microcontrollers, Arduino
    Replies: 0
    Last Post: 10-21-2015, 10:13 AM
  4. Dynamixel MX64T 3pin TTL and 4pin RS485 version
    By navidahmeduom in forum DYNAMIXEL & Robot Actuators
    Replies: 2
    Last Post: 05-27-2015, 05:42 AM
  5. Domino Logic
    By Matt in forum Off Topic
    Replies: 8
    Last Post: 07-21-2008, 08:57 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •