Introduction: Polydexter: Arduino Robotic Translation Arm
Polydexter was the introductory project in the Creative Architecture Machines (CAM) advanced options architecture studio at the California College of the Arts (CCA), taught by Jason Kelly Johnson (co-founder of Future Cities Lab) and Michael Shiloh. Parts developed for this robot would go on to become integral in the second project of the studio, our walking 3D printer Geoweaver, which can also be found here on Instructables. Other projects from the studio, as well as their accompanying Instructables, can be found at our Youtube channel.
Polydexter, designed and fabricated by Jia Wu and I, is a remote human-sensing Arduino-controlled robotic translation arm. Utilizing three axes of control, movements recorded by the input (analog) arm are augmented by the output (digital) arm, and produce a drawing. We enhanced the sense of remote control by hiding all of the electronics of the input arm and wrapped it in hand-glued chipboard while running all of the wiring beneath a 2x6 piece of lumber. It's hard to capture exactly how much fun Polydexter is to play with; appropriately, the robot required us humans to relearn how to write in order to get it's translations right (though Jia got very good at it and could write Chinese characters after enough practice!).
When we began this project we had no knowledge of Arduino or robotics and this was a great introduction to simple coding, electronics wiring, and the art of mechanical design. This is a simple but addictive toy to play with and is a great introduction to robot making. We still have fun messing around with it and are looking forward to hooking it up to Firefly to see how bringing in different machine vision or data sets can affect drawings. We extrapolated a lot of possible future uses: teaching people to write in different languages, translating/editing/censoring written messages between countries, or scaled up, translating a stroke of your hand into built space using precision brick laying or material extrusion.
Edit for Epilog Challenge: If we had access to a personal laser cutter we would prototype the begeezus out of this robot. We have many plans for new updates and tweaks that would incorporate much more refined, laser engraved parts out of acrylic and possibly Yupo.
Anyway, let's get Instructablesing.
Step 1: Materials and Equipment
- 1/8" acrylic, ~110 square inches
- 1/16" chipboard, ~300 square inches
- 2x6 lumber, ~3'-0" long
- Zip ties, ~30
- Screws for connecting servos to acrylic
- 3 potentiometers
- 3 servo motors
- Arduino Uno
- breadboard (or prototyping board)
- jumper wire
- soldering iron
For a list of used electronics, please refer to these custom made CAM kits from Oddwires.
Step 2: Laser Cut Parts
A laser cutter isn't required for the chipboard parts but it makes things much easier. Please rearrange the line work to fit your machine, and though we didn't want to mark the parts with numbering we color coded the parts to match to the assembly drawings.
Step 3: Build Analog (Chipboard) Arm
The analog arm basically glues together along the edges. We used simple tacky glue and the connections were strong. The colors in the cut DXF file correspond to the drawing above.
TIP: Piece it together from the inner layers out, adding the screws, washers and lock nuts next, and then gluing the outer layers on.
Step 4: Build Digital (Acrylic) Arm
The small holes in the acrylic are designed for use with zip ties. The major gear translates the 180 degree motion of the servo motor into 360 degrees. We used metal washers to smooth the friction between the acrylic pieces but you can also cut your own PETG washers. The colors in the cut DXF file correspond to the drawing above.
Step 5: Wire Arms Together
The wiring of Polydexter is pretty simple. The most complicated portion of the process came in requiring regulators for the MG995 servo motors that came with our kits. If you have servos that can be powered by a simple 5V power converter then you can skip the regulators. We apologize for our messy wiring and breadboard. In our defense, it was our first project and soldering the wires to the potentiometers was the extent of our capabilities at the time.
TIP: Back the potentiometers with some material to keep them attached firmly to the side of the chipboard. (Also, use washers, don't be lazy like we were!)
Step 6: Upload Arduino Code
The Arduino code is incredibly simple. Just make sure the angles correspond to the range of movement you like and you're good to go.
Step 7: Have Fun
Polydexter was a hit at our mid review, especially as it was one of the most interactive of the 2D drawing robots. One of our first ideas was a nod to Jia's Chinese origins as a tool that translates a subtractive process, pushing tea leaves in a sand box, into an inverted, tri-color, additive drawing. We just popped an Arduino in the middle of the translation process. We feel this idea of "translating" analog movements and enhancing or augmenting them through the robot is an exciting idea to explore, which is why Jia's crowning achievement for the Polydexter was to write 你好世界, or "Hello World."