An open source bike radar you can build yourself — a DIY alternative to the Garmin Varia.
No advanced electronics experience needed. If you can follow a wiring diagram and copy-paste code, you can build this.
- Detects vehicles or objects behind your bike using a small radar sensor
- Shows you how far away they are
- Warns you if something is getting closer
- Displays status on a tiny screen
- Beeps or vibrates when something is too close
Around 35–55 EUR in parts. Compare that to ~180 EUR for a Garmin Varia.
You don't need to understand all of these yet — just order them and we'll explain each one as we use it.
| Part | What it does |
|---|---|
| ESP32 (the brain) | A small computer that runs your code |
| LD2410 radar sensor | Detects movement behind you |
| OLED screen (0.96") | Shows distance and status |
| Buzzer | Makes a sound when something is close |
| 18650 battery + charger | Powers the whole thing for ~15 hours |
| Breadboard + cables | Connects everything together for testing |
Full list with quantities: hardware/bom.md
Radar sensor → sees something behind you
↓
ESP32 → figures out how close it is
↓
Screen → shows you the distance
Buzzer → beeps if it's too close
Follow the step-by-step guide: docs/build-guide.md
You don't need to read everything at once — just start at Step 1.
V1 — In progress
- Sensor reading works
- Detection logic done
- Risk levels (LOW / MED / HIGH)
- Screen showing status
- Alert system working
- Tested on a real bike
The Garmin Varia does basically the same thing and costs ~2000 SEK. It's also a closed system — you can't modify it, fix it, or understand how it works.
This project is fully open. Build it, change it, improve it.
MIT — do whatever you want with it.
See CONTRIBUTING.md