Location Accuracy
Landhopper: GPS Watch
Team B8: Gary Bailey, Twain Byrnes, Carson Swoveland
18-500 Capstone Design, Spring 2024
Electrical and Computer Engineering Department
Carnegie Mellon University
System Description
Minimalist GPS Smartwatch
Hikers are often forced to choose between good battery life on a less functional watch, or a GPS watch that must be charged every few days. Landhopper was designed to provide location data for lengthy outdoor trips without access to power or internet connectivity.
We aimed for 1 week of battery life and position tracking, and position measurement accuracy < 150 feet. Powered by solar energy, we attained ~10 days of battery life (depending on brightness) and 38 feet average position accuracy.
http://course.ece.cmu.edu/~ece500/projects/s24-teamb8/
Final Design
Verification and Evaluation
Conclusions & Additional Information
The hardware consists of two parts: the navigation subsystem and the power subsystem.
Energy
Harvester
Back Side of PCB
We tested Landhopper by taking it on a 2 hour hike through Schenley alongside a ZED-F9P RTK GPS module.
Location accuracy was almost entirely within 150 ft and battery voltage was maintained while the watch was in direct sunlight.
Landhopper is an all-in-one solution to issues of location tracking over long periods of time with its solar energy harvesting.
Future work may include making the casing weather resistant and reducing the size of the watch so that it is more comfortable.
Micro-
controller
GPS�Receiver
Battery Voltage
Landhopper
Solar Cell
As part of the final design we compared several distinct energy harvesting methods. We chose solar due to its ease of fabrication, small size, and high average power output.
Controller
Landhopper
True Path
Error
For the software, our tasks communicating over separate channels to log locations and load map data without making the watch unresponsive.
| Piezo | Solar | Kinetic |
Can Build? | No | Yes | Yes |
Power | N/A | 1-10mW | 1-5mW |
Size | Tiny | Small | Large |
Power Subsystem
Solar Cell
Boost Converter
ADP5090
3.3V Regulator
S-1317A33
Charge Controller
MCP73831
Battery
500mAh LiPo
USB Charging
System Power
Navigation Subsystem
Microcontroller
STM32L412
GPS Module
MAX-M10S
SD Card
Display
Sharp Memory LCD
GPS Antenna
User Controls
Joystick + button
Buzzer
UART
SPI
GPIO
Path Logging
Rendered
Tiles
Software Architecture
SD Card Task
Display Task
Button Task
GPS Task
Events
Tile
Requests
Position