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  1. Re: Inverse Kinematics of a Open-loop chain (SCARA robot arm)

    The question is how many degrees of freedom each joint has, and how many degrees of freedom you want to solve for the end effector.
    If you have only three degrees of freedom total, and only need...
  2. Question(s) Re: Serial Monitor keeps printing reversed question marks when using the DynamixelShield with UNO

    Also, don't remove a question just because it's answered. Others on the internet have the same question. If it's not preserved in the thread, google won't find it the next time around, and the cycle...
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    Re: RC100 data packets

    ~ is the C/C++ bitwise-not operator. Yes, this is "1's complement"
  4. Re: Connect servo dynamicel XL-320 to wizard 2.0 without U2D2

    What is the actual challenge here? You can't just use a 74241, you need a USB UART adapter, which shows up as a COM port in Windows. Then you point the Robotis software at that COM port. Then you...
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    Question(s) Re: Baudrate for dynamixels

    I just set return delay time to 0 or 1, no matter what the baud rate. I do add some parameter variation based on the specific joints; it's an interactive tuning exercise.
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    Question(s) Re: Baudrate for dynamixels

    Some microcontrollers need some time to turn around the RS-485 bus after sending the commands, so the return delay parameter makes sure the microcontroller has time to turn off the transciever and...
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    Project Re: Tachikoma by TheMaverick

    That sounds fantastic!



    Have you done the torque calculations? Will 9g servos be able to hold this design without overheating?
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    Question(s) Re: Baudrate for dynamixels

    If you need to ask about signal quality, then it's unlikely that the added fragility of 4.5 Mbps will help you at all compared to something safer like 1 Mbps.

    To know what "too long" and "too...
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    Re: Conversion between angle and position values

    Unless you truly need 360 degrees of motion (not 359.9) you don't need wheel mode.
    You should just center the formula for "sent parameter from desired angle" at 0 degrees == 2048 sent parameter....
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    Re: Conversion between angle and position values

    The 360 degree position is valued at 0. Unfortunately, you can't actually get QUITE to that position -- you'll get to (4095*360/4096) degrees. Protocol 2.0 has a "multi-turn" mode that may help if...
  11. Thread: Temprature

    by jwatte
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    Re: Temprature

    For hobby servos, I have no idea whether they even have a thermal cut-off, or if they just let you run them until they die?

    150F (about 65C I think?) on the actual core/windings of the servos is...
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    Question(s) 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...
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    Question(s) 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...
  14. Re: Is it normal that even with the same model, some dynamiels generate some sound?

    The rubber band has enough tension if you can pluck it with your finger and it sounds like "twang."

    Yes, torsion springs add more torque in one direction. But, if your robot is standing against...
  15. Re: Is it normal that even with the same model, some dynamiels generate some sound?

    Yes, that sounds exactly like an output that's under no load, and thus the PID controller is over-eager.
    Either add some load on the servo, or tune the PID to be sloppier (but then of course the...
  16. Re: Is it normal that even with the same model, some dynamiels generate some sound?

    The PID controller may be overshooting and re-correcting back and forth.
    Assuming this only happens when they're on, and torque is enabled.
    If you disable the torque, does the sound go away?
    ...
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    Re: OpenCM 9.04 and SPI

    In the Arduino API, "transfer" returns the byte that came back while it sent the argument byte.
  18. Re: Is it easy to change the adapter of those Robotis cables?

    Bob's Used Cars sell so many kinds of used cars and trucks, which one would you recommend?

    I recommend that you buy the one that seems to work for your application.

    If you have a hard time...
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    Re: Discharge rate of LIPO

    The difference between C=60 and C=75 doesn't matter at all.

    Also, at those levels, it's very likely the batteries are rated "optimistically" ("this is the largest possible current the battery...
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    Re: Discharge rate of LIPO

    The current capacity of a battery cannot "push" current into a circuit. The circuit draws as much current as it's designed/made to do at the voltage you provide it. If the power source cannot keep...
  21. Re: Is it easy to change the adapter of those Robotis cables?

    Net-like sleeves are called "cable sleeving" or "cable sheathing."
    https://www.mcmaster.com/cable-sheathing/
    https://amzn.to/30f5w8y
  22. Re: Is it easy to change the adapter of those Robotis cables?

    If you need custom cables, you'll want to buy the crimping kits for the connector series from the manufacturer, and your own wire to crimp the cables onto.
    The main challenge there is generally the...
  23. Question(s) Re: Attempting to send voltage to teenssy board via Arduino C++.

    I suggest the best forum to ask this in is https://forum.pjrc.com/forums/3-Technical-Support-amp-Questions
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    Re: Questions about powering

    Connecting the + pins on the batteries won't damage the motors, but it could damage the batteries, and perhaps the wiring between them, if the batteries are not charged to the same state.

    These...
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    Re: Reccomendations for a CS student

    Walking is quite challenging, mechanically. It sounds like a rover (wheeled robot) with sensors would be more up your alley.

    You might want to look into the Donkey Car approach? That's a...
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    Re: Questions about powering

    Correct. The system should have a single reference ground, will connected (low impedance.)
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    Re: Questions about powering

    Also: If you do use multiple batteries, you still have to have a shared ground (negative wire.) Don't forget that!
  28. Re: What are the pros and cons of buying the required number of Dynamixel at the same time? Your experience with Robotis return policy

    If you're going to build the robot, having all the servos at once might be helpful :-)
    Also, you save a little bit on shipping.
    On the other hand, if you're buying and shipping through customs,...
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    Question(s) Re: Connecting Dynamixel Motor to PC (Windows)

    Also: How are you powering the servo? The U2D2 can't power it itself, and an insufficient or flaky separate power source might cause problems.

    Does "recover servo firmware" in the Dynamixel Wizard...
  30. Re: [Beginner here with no experience] Need help with Ideas for implementing an automation process

    There are cases when I re-use fasteners.

    For example, when I assemble a 80/20 based trade show booth frame, I re-use the bolts and studs that go into the frame.

    When I re-hang a picture on my...
  31. Re: [Beginner here with no experience] Need help with Ideas for implementing an automation process

    If all you have is 4,000 fasteners (not 4,000 fastener TYPES) then you should do this manually. It'll take two hours, and then you're done.

    If you have 4,000 fastener TYPES that need to be sorted...
  32. Thread: Alan and Alena

    by jwatte
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    Project Re: Alan and Alena

    I wish you'd keep the camera from the front longer, and not cut away to the side so quickly :-)
    (Most youtube videos are under-edited, but not this one!)
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    Question(s) Re: AX12+ servos not recognized/seen

    Do you have a logic analyzer or oscilloscope?
    Can you verify the data being sent by the USB2Dynamixel?
  34. Question(s) Re: What is the best way to remove the horn of the Dynamixel?

    What I do for MX series servos, which works great, is:
    1) Remove the center screw.
    2) Screw in a bracket into the horn, using 4 screws at each 90 degree cardinal direction.
    3) Pull on this bracket...
  35. Re: Should we move Mech Warfare discussions to some other forum?

    There's some discussion going on here: https://forum.mechwarfare.org/
    So far, it hasn't fallen off the internet :-)
  36. Question(s) Re: Companies that make aluminum frames and thickness of 3D printed frames

    To make aluminum frames, the cheapest way is to make a watercut or lasercut shop cut them out of something bendable, like 5052.
    BigBlueSaw.com is one such company that can do that. You will then...
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    Re: First steps for Legavos

    Cool! The first walker I built was a three-servo variant, too!

    (You could also post a description on https://forum.mechwarfare.org/c/builds/6 and you'll get a forum "Builder" badge for it :-)
  38. Thread: mjbots quad A0

    by jwatte
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    Re: mjbots quad A0

    Looking forward to it!

    You should post it in https://forum.mechwarfare.org/c/builds/6 -- it'll give you a badge ;-)
  39. Re: Should we move Mech Warfare discussions to some other forum?

    Specifically, having a forum with history plus ability to keep uploads, doesn't come for free, anywhere.
    There's a "hosted Discourse" option, which is $100/month.
    Slack removes discussions after a...
  40. Thread: mjbots quad A0

    by jwatte
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    Re: mjbots quad A0

    pronking!

    What provides the most elasticity when landing? Feet, frame, belts, or PID loop?
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