Sawppy the Rover was inspired by JPL's Open Source Rover project. Most of the differences between Sawppy and its JPL inspiration were motivated by a desire to reduce cost and complexity. JPL's rover is designed for education, to be assembled by a school team and give a robust foundation for structured curriculum. Sawppy is more suited for individual hobbyists like myself who are happy to tinker and willing to make some trade-offs to lower cost.
The budget was $500, and getting there required the following changes:
- Motorization: Instead of using gearmotors with encoders managed by RoboClaw motor controllers, moving the wheels will be done with serial bus servo motors.
- Construction Method: Instead of using the Actobotics construction system, Sawppy will be built from Misumi 15mm 3-series aluminum extrusions beams connected by 3D-printed plastic parts.
These two major design goals can be summarized as: Servo Actuated Wheels, Printed Interconnect For Extrusion. The acronym SAWPIFE led to the nickname "Sawppy".
See the "Links" section for pointers to additional information:
- Live Onshape CAD file: This is where I'm tweaking and building Sawppy in full public view. Be warned the live file has upsides (latest ideas!) and downsides (latest idea doesn't work!)
- Github: This is where the assembly instructions currently live. It also has a snapshot of Sawppy components in STL file format. These parts may lag behind the live CAD data, but they have been printed, installed, and proven to work on my rover.
- Build Blog: The history of Sawppy, including stories of design goals and lessons learned from failures.
Since the time I declared Sawppy version 1.0 (mechanical foundation) complete and posted assembly instructions, others have built on top of what I've released to the world! They're outlined in the project log "Sawppy Builders" entries, page 1 and page 2 with more to come as I hear about more rovers.
Roger, I'm in the process of upgrading the controller on my Sawppy from an Arduino Mega 2560 to a Teensy 4.0 and am having an issue getting the serial communication between the Teensy and the LX16A servo board to work. I am using a bi-direction logic level shifter to manage the 3.3V to 5V level shift.
I've established the same setup works for other 5V serial devices such as a serial RC receiver, just not the servo board.
I have also found that I cannot get a response from the LX16A servo board when connecting to its serial port with a USB-to-UART bridge rather than connecting directly to the servo board's USB port.
I'm wondering whether anyone using this servo board for their Sawppy has seen similar issues?