I’m excited to announce the release of software version 6.1. This update includes several important improvements to robot performance and calibration:

• Enhanced acceleration and deceleration curves – Motion profiles are now smoother and more refined for improved robot control.
• Updated motor driver microstep settings – These changes not only complement the new accel/decel curves but also improve overall motion smoothness.
• Driver DIP switch update required – When upgrading to version 6.1, please update your motor driver DIP switch settings. Refer to the latest robot build manual (version 1.6), page 230 for the new settings. For users running earlier software versions, the previous DIP settings are still included on page 231 for reference.
• Improved calibration routine – Includes updated debounce logic to reduce calibration errors and prevent “calibration failure” messages.

Please download the updated manual and review the changes before installing the new version. As always, if you encounter any bugs or issues, let me know and I’ll work quickly to resolve them.

Thanks for your continued support, and I hope you enjoy the improvements in version 6.1!

https://anninrobotics.com/downloads/

https://huggingface.co/nvidia/GR00T-N1-2B

I'm selling a fully assembled AR-4 (Complete Electric Package + Robot Combo Kit), originally put together in Summer 2023. The arm has seen minimal use in an educational setting and is in excellent condition. I'm parting with it as I'm upgrading to a larger, commercially available robotic arm.

The setup includes:

AR-4 Robotic Arm (assembled and tested)

Complete Electric Package (stepper drivers, wiring, controller, etc.)

Version 1.5 Electronics Enclosure

Upgraded J2 Gearbox (from AR4 v1.6 – installed in 2023)

Upgraded J6 Housing + Gripper Mount (installed 2024 – compatible with MK3 gripper upgrades)

Note: The travel track shown in the photos is not included in the sale.

I am asking for $1750.

Happy to provide additional photos or video of it in operation. Feel free to reach out with questions! zseibold at gmail dot com. Located in central Vermont. Pickup preferred but would consider shipping domestically. Can meet between Burlington, VT and Boston, MA.

https://anninrobotics.com/wp-content/uploads/2025/08/AR-4-for-sale-in-Vermont.avif

https://anninrobotics.com/wp-content/uploads/2025/08/AR-4-for-sale-in-Vermont_2.avif

https://anninrobotics.com/wp-content/uploads/2025/08/AR-4-for-sale-in-Vermont_3.avif

https://anninrobotics.com/wp-content/uploads/2025/08/AR-4-for-sale-in-Vermont_4.avif

https://anninrobotics.com/wp-content/uploads/2025/08/AR-4-for-sale-in-Vermont_5.avif

3D print, PLA or PTEG, better use around 50%infill otherwise the screw head will crush the cover.

To install, drill 3mm holes, remove the M3x14 Philips pan head screws from the J1 limit switch and reinstall the cover on top of the switch using two M3x20 Philips pan head screws. Et voila.

STL file attached (as the .STL or .ZIP file does not upload, download J1 SW Cover STL.docx, rename it as .ZIP extract and you should get the STL file. Il not, contact me. I will also publish it on printables.

Regards

First time long time. Wanted to say first of all what a great project this is, big kudos to Chris and the community here keeping it going.

I'm putting together my first AR-4 using the aluminum kit. Some small challenges along the way but great learning. When I first booted it up, I was able to get motion and limit switches on all except two joints - no problem, I find it's some of my wiring. Among others the exposed J5 limit switch (waiting to tape it after testing) touched the aluminum causing challenges. Strangely at one point jogging J3 caused my whole PC to restart - possibly that short came through the USB and my computer responded?

Anyway, after re-working the limit switch and motor wires, I was able to get all 6 motors jogging and limit switches registering GRD/3.3v. I got the servo gripper together and popped that on as well.

Excited to get into calibration, I started up the software and notice the encoder values don't update anymore! This is bizarre because I hadn't touched any of their wiring. Simply when I run the Test Encoders program, all values stay at 1000 whereas before I could move them up and down by manually moving the joints as expected.

I unwired ALL the encoders and connected J1 encoder directly into the BLK/RED into 5V/GRD and BRN/BLU directly into pin 14/15. Still no encoder reading when I run Test Encoders for J1 as I move the joint left and right.

Unfortunately I don't own an Oscilloscope. With my multimeter I don't read any voltage between BRN or BLU vs GRD, which concerns me. I get ~3.6v between GRD and Encoder GRN or ORG, but I can't get the voltage to change moving the joint manually, so not sure what that reading means. Perhaps my tool can't pick up the microchanges in voltage, or perhaps something is more wrong.

I haven't yet tried to unwire and re-wire the other encoders that run through the Cat6 extensions, though that's my next step in mind. I just figured that going directly to J1 would eliminate some of the potential wiring challenges.

I guess I have a few questions for Chris and the community:

• Is it possible that I fried all 6 of my Encoders at once through some boneheaded mistake or short or ground? Without an oscilloscope is there a reliable way to test that they have not failed? (I'm considering buying a scope if needed)

• If my Encoders aren't all broken, should I consider an alternate wiring? Or are there encoder changes to consider? I assume the Teensy reading of A+ and B+ makes the most sense, and if those don't read A-/B- and Z aren't going to be a lot of help.

• If my Encoders have all failed, any thoughts on replacement Encoders or after-market Encoders (once I lick my wounds about the damages)? Stepperonline doesn't have a lot of documentation on the onboard Encoders or troubleshooting, so curious folks' thoughts on encoders generally for Steppers.

• I guess as a corollary, have folks run the AR4 primarily on Open Loop? Any disadvantages other than the obvious lack of clear position detection?

Sorry for the long post, I tried searching the forums and online but have been running into dead ends. Any help is appreciated!

I'm trying to determine whether this behavior is due to my specific build or if it’s a software/control limitation inherent to the AR4 system.

have anyone observed similar behavior in AR4 builds? Any insight would be appreciated.

Thanks!

Alon.

https://www.youtube.com/watch?v=0FqDah2KEOc

End Effector with laser crosshair