LEGO Robot Inventor 51515 Rubik's Cube Solver

UPDATE: The method used to load the program into Mindstorms hub does not work with latest firmware. I have fixed it by using the same method used in MindCuber-RI. The whole thing is written by David Gilday anyway and all the credit goes to him. Thank to Charles and Michal for testing the updated loading method. Running a new version is similar to loading of MindCuber-RI shown here:    • How to start MindCuber-RI Rubik Solve...  

A Rubik's cube solver based on the great design by David Gilday (mindcuber.com). Thank you, David!

My son (10) has done the mechanical part by using PrimeCuber instructions and (only!) the Robot Inventor 51515 parts. I am more than satisfied with the results. :)

Obviously, some people have liked the design a lot. :) Greta Galli made a nice video showing more detais:    • IL ROBOT CHE TUTTI VORREBBERO (credo)...   and Orione (http://www.orione-alnitak.eu/responsive) made instructions: https://drive.google.com/file/d/1bPBp...

If it is not corrected yet, in the instructions it says "Original concept: Mladen". Well, not really. The original concept is by great David Gilday. My son Marin has adapted the Prime build and I have adapted the code.

You can find Mindstorms 51515 code for this build in a GitHub repository: https://github.com/mycropht/PrimeCube...

You should read the instructions included in the GitHub README.txt. In case of scanning problems, you could try the updated program for testing (CubeTestScan).

The Python code is copied from the LEGO SPIKE app to the Mindstorms app. I have installed the LEGO Education SPIKE app, opened PrimeCuber projects (without connecting the hub) and C&P-ed the code to empty Python projects in Mindstorms app.

The main code worked with the Mindstorms FW but the parameters for the scanning arm had to be changed as the design is quite different than the original (the part 6302830 rack 13M is missing in the 51515 set). The large solving table could not be loaded for some reason, but I have not investigated as it is optional, and the solving is fast enough without it).

You need the following files from the GitHub repo: PCRISolver-v1p4.lms, PCRIInstall-v1p4.lms, PrimeCuber-RI-v1p4.lms

There is also a photo album with some pictures: https://photos.app.goo.gl/BWX9FABtCkd...

If you add a photo of your build to the album, my son and I will appreciate it. :)

Some troubleshooting info:

After the solving program is started, the left/right buttons on the hub can be used to correct the cube cradle position - before a cube is inserted.

The cube used in the video is "Giiker M3" (supposedly a Xiaomi brand). It has magnets so it snaps properly in the position every time. Magnets really help!!! Apparently, there is also a Bluetooth version of the cube, but it is not necessary.

After the solving program is started, a pixel will be lighted near by the offending port if the expected motor/sensor is not found.

If there is a problem with scanning or tilting the cube, check if the cube cradle is in the right position. If it is one hole closer to either scanning or grabbing hand, the scanning and tilting almost work.

We had a case where the color sensor cable was too tight. Also, the top of the grabbing hand can be made almost right, but not quite.

The most common problem is with scanning. If the cube cannot be scanned properly, after three tries an up-left arrow will appear. The problems are typically mechanical. Do not worry there is no orange among the "standard" colours as the scanning uses RGB values. Also, the big LED colours do not correspond very well to the colours on the cube.

If there are scanning problems, it should be checked if the build is solid enough on the gears side. The gears should not skip. Sometimes, more or less light leads to more accurate scanning.

If there of scaning or cube tilting problems, there are some tips at the end of the video showing the old (obsolete) unstalling procedure:    • Follow - up: LEGO Robot Inventor 5151...  

The scanning arm movements are quite jerky. In case of scanning problems, maybe a rubber band fix will help. There is a picture in the photo album where a face mask band is used to tension the arm a bit.

I hope this helps. Please let me know in the comments if you build it and it works! :)

Update: David Gilday (the MindCuber designer) has finished the new version built for the 51515 set and using all 4 motors (!). You can see it in action here:    • MindCuber-RI - Rubik Solver for Minds...