Introduction: 3D Printed Raspberry Pi Tablet and Cradle for VEX Practice Fields
I am a high school senior in McLean, VA. I chose to design and assemble a 3D printed Raspberry Pi tablet along with a custom VEX tower attachment for use in my school's robotics lab.
My school is part of the VEX robotics program, a competition based robotics organization that aims to teach students about STEM. Over the past few years we have been using a system for running test matches in the lab that has always been difficult. It requires a dedicated Windows system to control the matches that you have to manually start from the other side of the room which typically requires a member of a robotics team to man the control center while the match is taking place. I wanted to create this tablet so that we can manage the matches while on the field without the use of this distant computer. In addition, I wanted to design a cradle for the tablet that would hold it on one of the control towers for the robots.
My end goal was to streamline the practice match setup so that we can spend less time controlling the field and more time practicing for our next tournament. This Instructable serves as documentation behind the project from start to finish.
I would also like to give credit to Adafruit for their very helpful tutorial which I am using as a base for my project.
Step 1: Plan and Design the Tablet
Before I even started on the tablet creation process, I ordered all the parts I needed for the assembly. I figured that way there would be little to no waiting time during my project. Here are the parts I needed for the tablet in addition to the 3D printer which I was fortunate enough to use at my high school: https://docs.google.com/document/d/1aDcrgIz1femjis...
So after the parts were ordered I then started to look into the 3D designs for the tablet framing and casing. I used SketchUp to preview the 3D templates for the tablet. Since the tablet files are in .stl format I needed to install the STL Plugin for SketchUp here: https://extensions.sketchup.com/en/content/sketchup-stl. You are able to modify the files that you import but I ended up not changing them as they were well thought out and designed.
Lastly, I started to design the first version of the cradle for the tablet. I did pause on this step until I finished the tablet however. I finished the prototypes later in the project.
Step 2: Start the Printing!!
Once I opened all of the 3D files in SketchUp, I then started to print the pieces using a MakerBot Replicator z18 using standard settings. Printing all the pieces took a total of about 6 hours. Once the parts are printed you can move on to the assembly of the tablet.
Step 3: Assemble the Tablet
Although I recommend following the instructions closely on the Adafruit website (as they are very detailed), there are a couple of things I want to point out about the whole process. I also included several pictures showing you my assembly process.
If you haven't soldered before (and I recommend taking the time to practice before you start the soldering process) it can be particularly difficult with this project. Part of the soldering job includes soldering wire to the Raspberry Pi's GPIO pins which can be tricky. I had to solder and desolder then solder again in order to successfully transfer power from the Powercore 1000 to the Raspberry Pi. With patience, hopefully you can complete the soldering better than I did initially.
#2: Freaking ribbon cables
In the assembly there are a few ribbon cables that need to be attached, some connecting the display to its board and another one connected the board to the Raspberry Pi. Ribbon cables can be very frustration to deal with because they are small and need to be fastened with a little plastic piece to each board. My suggestion is again to use patience because the ribbon cables and the plastic pieces can break fairly easily. In fact, the plastic piece connecting the ribbon cable to the Raspberry Pi display board did break during the assembly process. So again patience is key. Also don't forget to attach the ribbon cables in the correct orientation. If the contact points on the cable don't match up to the contact points on each board, the display will not be recognized by the Pi.
#3: Slide switch installation
I realized that the area for the switch on the print is not small enough to totally secure it in place in the tablet so I had to use some hot glue to keep it in place. Although I recommend using hot glue (and you only need just a tiny dab of it on the bottom of the switch) you can use any material that will keep it in place.
Step 4: Finish the Tablet Cradle
Over the course of the project I made 2 versions of the tablet cradle.
After the first version I had major problems with the sizing as the tablet couldn't even fit into the cradle and the screw holes were not lined up right. Also, the bottom of the base was too wide to be mounted on the tower. I used the dremel to figure out how I needed to modify the base of the cradle so that it could fit on the tower and figured out how big I needed to make the next version of the cradle. When I made the necessary changes, the cradle was able to fit the tablet and was easily mounted to the tower. I have a feeling I will change the cradle design in the future though.
Step 5: Install Exagear Desktop and Run the VEX Field Control Software
To control the field I had to use Windows emulation software called Exagear Desktop to run the VEX application that is supposed to be used on a Windows based machine. It costs around 27 dollars to use it for the Raspberry Pi 3 and it is well worth it as the software runs very well. It also comes with easy to follow instructions on how to set it up.
However, at this stage I am currently unable to control the field because the tablet does not properly recognize that the controller for the field is plugged in. I am in the process of resolving that issue so that I can finish the project.
Step 6: Finished Product and TBD!
I hope to refine my tablet and stand over the course of the next few weeks so stay tuned for more updates and changes. I have attached a few images of the finished product.