Hands-free LED bicycle jacket (2013)

This project was completed for Physical Computing course in Human centered design & engineering Master's program at University of Washington.

My role: Identified problems and opportunities, researched competitive landscape and technologies, and designed and built a prototype hands-free LED bicycle jacket to enable bicyclists to signal while keeping hands on handlebar. The jacket increases bicycle safety by allowing bicyclists to keep both hands on brakes while signaling turns, slowing down, or pointing out road hazards when riding in a group.

Problems

Bicyclists use hand signals to indicate turns and stops. Signaling with hands affects safety of bicyclists as they can't signal with hands and stop at the same time. Bicyclists may need both hands to steady a bicycle under hard braking.

When riding in a group formation (peloton), the lead bicyclist uses hand signals to point out road hazards in addition to signaling for stopping & turning. Bicyclists in the back of a group may not see signals from the leader if their view of the leader is blocked.

Process

After identifying problems and opportunities, I created a vision for the product after researching existing technology for signaling, hands-free input, and microcontrollers for processing I/O. I also researched the landscape of related projects:

Prioritizing features

After creating a vision for the product, I proposed a product roadmap based on customer needs and my expertise.

Phase 1: Minimum Viable Product
LED strip
Force sensitive switch in a glove that turns on LED turn signals
Accelerometer triggered LED stop light

Phase 2: Additional features
Hazard LEDs on sleeve
XBee wireless communication between 2 prototype jackets

Hardware development

fritzing circuit prototyping software was used to plan the initial breadboard prototype. The following diagrams illustrates how accelerometer, LEDs, force-sensitive resistors, buttons, and resistors were wired on a breadboard.

Challenges encountered

Choosing LEDs that are daylight visible at a distance for turn signal & stoplight

Jacket with LED strips taped on

A digital RGB LED strip was chosen because of the flexibility to bend to the shape of a person's back and the ability to individually control the color of each LED

EL wires were rejected due to lack of daylight visibility
Luxeon LEDs were rejected due to complexity required in heat dissipation and lens

Designing turn signal switches that can be easily accessed by rider while minimalizing interference with riding bicycle.

After iterations, the button to trigger turn signals was placed on a glove, triggered by tapping thumb against base of index finger. This gesture was selected as it can be accomplished while hand maintains grip of handlebars. Pressing button turns on turn signal for 5 seconds, while holding button turns on turn signals indefinitely until canceled by another press. Keeping turn signals flashing can be used when increased visibility is desired, such as when stopped on side of road.
Mounting buttons/switches on the bicycle is undesirable as it ties jacket to a specific bicycle.

Powering LED strip and Arduino from a single battery

The final prototype uses a single battery and single regulator to power the LED power strip and Arduino. Details of how to power the Arduino and secondary circuits are in a separate blog post Powering Arduino and secondary circuits.

Prototype with a DC voltage regulator module and 6x AA battery holder: