Forum Posts

matthew
Apr 28, 2021
In General Discussion
I'm looking to develop more fluid/complex moves for my AR3 and I also intend to develop some custom multi-axis, sensor driven, interactive mechanisms for more artistic endeavors. My CAD and mechanical design skills are rather strong, but my control skills which are limited to a few solid years of tinkering with Arduino. I have seen a few posts from users that are operating their arms with ROS/MoveIt and RoboDK which look promising, but I'd like to build up my knowledge base before pursuing either of these options. It seems like ROS might be the best option given its widespread adoption and community support, but I'd like to hear from some of the more seasoned users and get their opinions. Are there any reference websites/books/projects that might be helpful as I start this process?
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matthew
Apr 11, 2021
In Questions
I've seen several threads regarding how to power the Teensy 3.5 and noticed the recent updates to the assembly manual that get to a workable solution. Has anyone tried to cut the pad on the back of the teensy to disable the PC supplied 5V and power it directly from the 5V supply? CAUTION: If you try this without cutting the pad, would could fry your computer's usb port which might be the reason why this is not in the manual... Has anyone tried using level shifters to boost/step down the 3.3V pins on the teensy to 5V for the encoder/switches? This would also let you use the teensy 4.1 which is not 5V compliant, but 5 times faster than the 3.5. These have worked great for me in the past with 3.3v teensy boards https://www.adafruit.com/product/757
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matthew
Apr 11, 2021
In General Discussion
I just got my aluminum AR3 up and running yesterday. I was/am getting tons of interference on my encoders and limit switches. This is manifesting in frequent erroneous reported limit/home switch closures and the motor position readings moving while the robot is at rest. I switched all the motors to open loop on the calibration page, and moved some of my cables/wires around. I noticed that the instructions did not call for grounding the shielding cable on the encoders and that the home switches have zero shielding and run parallel to unshielded stepper motor cables. I invite anyone who has worked through this issue to offer some simple advice/best practices that might eventually work there way into the extensive assembly document.
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matthew
Apr 11, 2021
In General Discussion
I just got my Aluminum AR3 up and running yesterday and I noticed that the global cartesian moves were a few degrees off of where they should be. It seems like this is due to the homing operation and variations in switch location/performance. I will likely switch over to inductive switches in the near future, but this seems like a good general topic for discussion. I have not found any threads that directly address this issue. I'm looking for advice on: How to adjust the "software zero" such that the robot is actually where it thinks it is and the inverse kinematics work properly. The variation in switch locations from build to build could easily vary by a few degrees. Has anyone developed a good procedure for calibrating this zero? I have some ideas, but would love to hear from anyone who has gone through this process. I'm linking to this thread, because it is awesome and I expect it to be very beneficial towards improving the initial calibration of the arm on startup. https://www.anninrobotics.com/forum/general-discussion/ar3-hardware-mods
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matthew
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