🚴‍♂️ Automatic Bicycle Light

open-source-project with an STM32C011, mpu6050 and 3d-printed case. Switches Light on when bicycle moves. Switches off after 1 minute standing still.

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Features

• Movement detection via MPU6050 (measurement each 2 seconds)
• Automatic On when movement detected, Off after standing still and timeout
• STM32-based (STM32CubeMX IOC included)
• 3D-printed case
• Low sysclk for low power consumption: ~1mA idle current (mcu + mpu6050)

Overview

• Technical Stack
• Quickstart
• BOM
• Build Instruction
• Firmware Flashing
• License Overview
• Known Problems
• Contribute

Technical Stack

Component	Technology
MCU	STM32C011 (STM32CubeMX IOC)
Sensor	MPU6050 (I²C)
Case	PLA, STL-Files
Firmware	STM, MIT-licensed

BOM

Component	Reichelt No.
STM32C011 mcu	STM32C011J6M6
mpu6050	DEBO HMC5883L 2
step-down converter	LMO78_03-1.0
Adapterboard SO8	RE 899
BC547, npn bjt	...
1k THT base resistor	...
M3 countersunk screws	SKS M3X20-50
M3 hot melt insert thread	...
cable tie	SHVP BS18-10002

• for flashing: ST-link V3 or eval board (like NUCLEO-F746ZG)
• lipo battery, case works with 3S battery from an RC-Car (102mm x 34mm x 23mm)
• front and rear LED light (e.g. battery powered light from a supermarket/hardware store)

Quickstart

1. Build Hardware: solder MCU on SO8-Adapterboard if needed, print STLs (0.2mm Layer, 20% Infill)
2. Flash firmware: ST-link V3 or STM-eval board
3. Connect: Connect to LiPo battery and front/rear light
4. Test: move bicycle → Lampe ON, 1min still → OFF

STLs: mechanics/

Build instruction

1. 3D-Print

Case: mechnics/bicycleLight_case_r2.stl (Supports: No)
Cover: mechnics/bicycleLight_cover.stl
Printsettings: 0.2mm, 210°C extruder, 60°C heat bed

2. Adapter PCB

use SO8 adapter pcb if needed

3. Cabling

Name	SO8 pin no.	STM gpio name
LED-Light transistor	→ Pin 1	PC14
MPU6050 SDA	→ Pin 5	PA8
MPU6050 SCL	→ Pin 6	PA12
SWDIO (flashing)	→ Pin 7
SWCLK (flashing)	→ Pin 8

Flashing Hardware

e.g. ST-Link V2/3 or STM eval kit:

• NUCLEO-F303RE (reichelt, not tested)
• NUCLEO-F746ZG (tested)
• NUCLEO-F446ZE (reichelt, not tested, but same base as F746ZG)

on MB1137 based eval boards (F746ZG, F446ZE, etc.) connector (CN6) can be used to program MCUs. headers on CN4 needs to be removed to use external programming (not the mcu on the eval board). pinout of the CN6:

CN6 pin	connect to STM mcu	function
1	→ Pin 2	Vdd feedback (connect here also 3V3 from the eval board to power the external MCU, e.g. pin 7 from CN8)
2	→ Pin 8	SWCLK
3	→ Pin 3	GND
4	→ Pin 7	SWDIO
5	n.c.	NRST
6	n.c.	SWO

Firmware Flashing

use STM32CubeProgrammer pre-built elf in binary folder

• connect
• choose Erase & Programming
• browse to the binary folder and choose the elf file
• Start programming

License Overview

Component	License	Files
Firmware (own)	MIT	firmware/
STM32CubeMX Code	BSD-3-Clause	*.ioc, generated HAL-Code
STLs/Case	CC-BY-SA-3.0	mechanics/
Images	CC-BY-SA-4.0	images/

See LICENSE.

Known Problems

• waterproof: not perfectly waterproof. mount with cover at the bottom to be waterproof against rain at least.

See Issues.

Contribute

1. Fork this Repo
2. Create Feature-Branch (git checkout -b feature/mpu-opti)
3. Commit your changes (git commit -m 'MPU Optimierung')
4. Push (git push origin feature/mpu-opti)
5. Create Pull Request

Acknowledgments

• MPU6050 Motion-Detect Tutorial
• OSHWA License-Helper

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⭐ Star this Repo, if it helps! Questions? Issues

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*© 2025 mle *^{12 345678910}

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Footnotes

1. https://github.com/othneildrew/Best-README-Template ↩

2. https://github.com/dbader/readme-template ↩

3. https://github.com/matiassingers/awesome-readme ↩

4. https://github.com/topics/readme-template ↩

5. https://gist.github.com/DomPizzie/7a5ff55ffa9081f2de27c315f5018afc ↩

6. https://github.com/cfpb/open-source-project-template/blob/main/README.md ↩

7. https://dev.to/sumonta056/github-readme-template-for-personal-projects-3lka ↩

8. https://github.com/sfbrigade/data-science-wg/blob/master/dswg_project_resources/Project-README-template.md ↩

9. https://www.reddit.com/r/programming/comments/l0mgcy/github_readme_templates_creating_a_good_readme_is/ ↩

10. https://www.daytona.io/dotfiles/how-to-write-4000-stars-github-readme-for-your-project ↩