396eeb175e
- content/edge/l3/edge-car-tracker.md, written from the evidence notes - product image of the SIM7080G Cat-M module, cropped to 640px, with a caption naming what it is and that it is a product image - referenced from the edge overview - original kept in sam/CAR_GPS_TRACKER so the project repo documents its own build
2.3 KiB
id, area, level, title, claim, confidence, period, tech, metrics, artefacts, public, last_verified, tags
| id | area | level | title | claim | confidence | period | tech | metrics | artefacts | public | last_verified | tags | ||||||||||||||||
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| edge-car-tracker | edge | 3 | Artefact — Vehicle tracker on LTE Cat-M | A tracker that sleeps between reports · wakes on a schedule or when the car moves · and reports when it leaves a boundary set from the web interface. | in-progress | 2024– |
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true | 2026-10-28 |
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The build is on the bench: two LiFePO batteries, a buck converter, an ESP32 with GPS, and a cellular module for the uplink. The car keeps the packs charged while it is running.
What it does
Two behaviours, chosen by the settings rather than hard-coded. When the car is parked the ESP32 sits in deep sleep, wakes on a timer, checks its own configuration, and reports only what the settings ask for. When the car is moving it stays awake and reports on a shorter interval. Either way the interval and the boundary can be changed from the web interface, and a change can force an immediate update rather than waiting for the next wake.
The geofence is the part that matters. A boundary is drawn from the web interface, and the device is responsible for deciding whether it has left it — which is why the settings have to travel to the device rather than live only in the server.
Why LTE Cat-M rather than WiFi
The tracker lives in a car. WiFi coverage is a driveway, not a road. Cat-M and NB-IoT were chosen because they are designed for exactly this shape of traffic — small payloads, long sleeps, coverage beyond what 4G handsets need — and because the modules are cheap enough to leave installed.
What it proves
A complete path rather than a demo: constrained hardware, a power budget that dictates the schedule, a device that holds enough state to act on its own, and a web application that configures it and shows where it has been.
Still open
Field testing across the full battery cycle. The sleep interval that is right for a parked car and the interval that is right for a moving one are guesses until the discharge curve has been measured over a week rather than a day.