From Mobility to Mowing: Hacking Surplus Medical Equipment for an Autonomous Lawnmower
Imagine an autonomous lawnmower, precisely navigating your yard with no human intervention. Now, imagine its heart and soul is a repurposed electric wheelchair. This is the premise of a fascinating project where a Jazzy Select Mobility Scooter Wheelchair is transformed into an autonomous mower. By hacking its control system, Brent is leveraging the scooter’s robust drive motors and motor controller for a completely different purpose.
The Heart of the Hack: The Joystick Interface
The core of this project involves reverse-engineering the wheelchair’s control system. The key is its three-pin interface, which consists of a 24V battery line, a ground, and a single unidirectional communication line from the joystick to the speed controller. The primary challenge was to replace the physical joystick with a microcontroller that could send the same commands.
To achieve this, an Arduino was used to emulate the joystick. A Crystalfontz display with a BridgeTech Eve graphic chip proved invaluable for visualizing and decoding the data packets sent by the original joystick. This setup allowed the Brent to decipher the specific serial commands needed to control the scooter.
Decoding the Scooter’s Language
The communication protocol is a serial packet operating at 38.4 kilobits with 8 data bits, even parity, and one stop bit. The project focuses on a five-byte packet that dictates the scooter’s movements. Each byte serves a specific function:
- Byte 1: Status (e.g., speed limit, direction).
- Byte 2: Speed range.
- Byte 3: Forward/backward control.
- Byte 4: Turn control.
- Byte 5: Checksum (for data integrity).
By manipulating the values within this packet, the Arduino can precisely control the scooter’s forward, backward, and turning movements. The project’s code, which generates these packets, is available for others to learn from and build upon.
The Future of the Jazzy Mower
The ultimate goal of this project is to integrate the hacked control system with ArduRover, a popular open-source platform for robotic vehicles. By adding a GPS module, the system will be able to navigate autonomously. The final phase involves mounting a gasoline engine and a two-blade deck onto the scooter’s chassis to complete the transformation into a fully autonomous lawnmower. This project is a testament to the power of reverse engineering and creative problem-solving, turning a piece of medical equipment into a lawn care robot.
Jeffrey Nystrom is an engineering technician at Crystalfontz. He graduated from ITT Technical Institute of Technology with his B.S. in Electronics Engineering. In his position, Jeff engages in customer technical support, works on engineering projects, and supports Crystalfontz’s manufacturing operations. Outside of the office, Jeff enjoys working in his shop, tinkering with his 3D printer, and going on new adventures with his family.
