Bike Turn-Signal Backpack with an LED Matrix
Handlebar buttons show bright arrows on your back so drivers know where you are turning.
A 16×16 addressable LED matrix is bright enough to see in daylight. An ESP32 animates left, right and brake patterns, triggered by wireless buttons on the handlebar.
This adds visibility but does not replace hand signals, lights required by law or a helmet.
Mission steps
Mount the matrix
Sew or strap the matrix to the outside of a backpack behind a diffuser panel.
Wire power and data
Matrix 5 V/GND from a power bank, data from an ESP32 GPIO through a 330 Ω resistor.
Add the buttons
Use a second ESP32 on the handlebar sending ESP-NOW messages, or a wired cable.
Animate
Draw blinking arrows with FastLED or WLED presets; add a steady red pattern at night.
Test visibility
Check it from a car's distance in daylight and adjust brightness and current limits.
Questions
How long does the battery last?
At 20% brightness a 10,000 mAh bank lasts several hours. Use the Power Budget calculator with 60 mA per LED at full white.