Project tutorial
Bluetooth-Enabled Bicycle Turn Signal

Bluetooth-Enabled Bicycle Turn Signal © MIT

Are you tired of sticking your arms out to indicate which direction you're turning?

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Components and supplies

Ard nano
Arduino Nano R3
Or an ATMEGA328P on a PCB
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HC-05 Bluetooth Module
8x8 LED Matrix with MAX7219 driver
Lithium-ion power bank (or battery with 134N3P chip)
Waterproof enclosure/case
Toggle switch (ON-OFF-ON SPDT)
on-off-on for turn signal and on-off for power switches
Adafruit industries ada592 image 75px
USB-A to Micro-USB Cable
Any USB-A cable with a 5V and ground wire will do
Dupont connector and some wires
12002 04
Breadboard (generic)
Or PCB for slimmer enclosures
Qi wireless receiver
Mfr 25fbf52 221r sml
Resistor 221 ohm
pulldown resistor

Necessary tools and machines

09507 01
Soldering iron (generic)
Hy gluegun
Hot glue gun (generic)

About this project


After commuting to work every day on my bicycle, I decided that I needed a better way to signal my turns. Sticking my arms out can be dangerous, especially if you're riding downhill in the rain (as is common in Vancouver).

I had recently got an Arduino and wanted to embark on my first project, so I decided to kill two birds with one stone!

I wanted something waterproof that I can use in the rain, and something detachable so it wouldn't get stolen, it needed to be detachable/wireless.

The plan was to have a couple of switches embedded into the handlebars (for power and for turn signal), use a Bluetooth transmitter (HC-05) for communication, and have an Arduino Nano to control it all with an 18650 lithium-ion battery (controlled with a 134N3P chip) for power. On the other end of the bike, there are two 8x8 LED matrices controlled by MAX7219 controllers, a Bluetooth receiver (HC-05), an ATMEGA328P chip to control all the components and an 18650 (or 14500) lithium-ion battery for power. I also added a Qi wireless charging receiver to charge the battery without opening the lights enclosure.

Action shots

Here's a video!

Video of the setup in action

A closeup of the case with all the gubbins:

If you don't like my boring arrows, make any indicator animation you want using my 8x8 LED byte generator found on my Github:


Wiring diagrams

Diagram for handlebar/controller:

Diagram for the lights:

Setup instructions:

  • Set up the HC-05 Bluetooth modules to pair with each other using a master-slave setup (instructions).
  • Other Bluetooth modules with similar functionality can be used.
  • Upload code for the lights and the handlebars to the Arduino Nano (or any other ATMEGA328P based chip).
  • Wire everything up according to the wiring diagrams.
  • if using a reed switch to control power to the lights, you'll need a magnet.

Variations/upgrade ideas:

  • Reed switch to control power to the lights. If your case is too slim for a toggle switch (like my latest iteration) or you're worried about the waterproof-ness of the case, a reed switch could be used.
  • A magnet attached to the light mount can turn the lights on and the lights can be turned off by taking the lights off the mount.
  • Or a second magnet can be used to change the flux path and open the reed switch like so:
  • Neopixel rings and jewels as a turn signal, like a car with the outer ring in red and the inner jewel lit up amber and flashing when turning.
  • Add an accelerometer to detect slowing down and display a slowing down animation or flash amber lights.

Pictures of the build:

Internals leaking out:

Note: Bluetooth module, Arduino Nano and PCB separated from battery by a long ~1m cable

Testing lights before gluing everything and closing the case:

It's working! Time to mount it to my bike:

Message me for more details if you want to make one for yourself.

Thanks for reading!

Old (thick) setup pics:




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