Automatic Bike Brake Light

thingiverse

This is a self-powered backlight for electric bicycles that operates without manual switches, utilizing an accelerometer to detect braking motion. The software can be accessed on GitHub at https://github.com/ChristophPech/BrakeLight. A Mosfet powers the LEDs, while Arduino's PWM regulates brightness during normal operation and braking states. The accelerometer samples data at 2kHz, accumulates it to 10Hz, and applies a band-pass filter to eliminate noise (low-pass) and align with standard orientation (high-pass). Users can employ any logic-level Mosfet; though pull-down and gate resistors are not necessary, they may prevent glitches on low-cost clones like the Chinese nano variant. The status LED is optional but helpful for confirming functionality. The Arduino's voltage handling capacity is limited to 12V; a 5V DC converter might be required depending on input voltage. Suitable components include an Arduino Nano (or Mini or Micro), N-Channel logic-level Mosfet (e.g., RFP30N06LE), 12V COB-Led module (e.g., Sumbulbs ), Adxl345 (Sparkfun breakout), and red rectangular back reflectors.