Turn Signal Gloves

Designed and prototyped in my free time, these touch-activated turn signal bicycle gloves dramatically increase road presence while facilitating effective road communication on the fly.

 

The end mission for these gloves is to encourage decreased dependency on motor vehicles. By promising increased visibility on two wheels, these gloves aim to replace car trips with bicycle commutes by boosting the popularity of practical urban cycling. 

Design Requirements

I chose to mount turn signals on a pair of gloves to maximize visibility (hands can be extended far away from the centerline of the bike), and eliminate the need to install systems on a bike, or transfer systems between bikes. Given that I would be vetting the prototype, and that I ride every day, year-round, in the urban setting of Denver, Colorado, these gloves had to satisfy a few key requirements:

  • Fully waterproof
  • Visible from ahead and behind
  • Able to be activated easily with a single hand, allowing one to remain on the handlebar
  • USB rechargeable
  • Battery to last for a week of daily use, even in cold temperatures
  • Sufficiently bright for daytime use

Design Process – Circuit Board

Motorists are accustomed to flashing turn signals, so these gloves must play along. To that effect, I designed and built my own square wave generator out of two cross-coupled flip-flop circuits, laser cut then chemical etched onto blank PCB board.

First-generation PCB, fresh from the laser cutter. All visible copper will be chemically removed.

The PCB after etching, with all circuit elements soldered. Capacitors, resistors, and transistors create the flashing pattern and determine the flash rate (I settled on 2.0 Hz).

The initial circuit board was too bulky for a wearable item, but allowed me to dial in my flash rate and focus on size optimization with subsequent iterations. I used SMD components and more strategic circuit architecture to reduce thickness by 60% and surface area by 25%.

Second-generation PCB designed for SMD components reduces thickness dramatically.

Final PCB iteration, hand-soldered under a microscope. Small adjustments to layout further reduce overall surface area. The height difference compared to the original design is substantial

Design Process – Housing

Designed for everyday use, the glove’s battery, charger, and circuit board must package tightly in a housing that is waterproof, conforms to the hand, and accommodates micro-USB charging.

Hand contour

The base of the housing was modeled to conform to the hand by first sketching over scaled images of a gloved hand. This image is taken from the knuckles looking back to the glove wrist strap.

Test fitting

Simple 3D prints were used at this point to optimize the hand contour and electrical component layout to maximize comfort and minimize footprint, while allowing convenient access to the battery charger.

CAD concepts

Initial housing designs were clumsy, bulky, and required an awkward top cap to be waterproof. The CAD model was convoluted and difficult to optimize for improvements learned through prototypes.

To better optimize housing size and increase the ease of adjusting and refining the model, I turned to top-down modelling techniques. The resulting SolidWorks model was robust and easily edited, and how best to enclose the battery, charger, and PCB became a no-brainer.

Master sketch

The top-right sketch group primarily controls the top profile of the housing; the central sketch group primarily controls the footprint, including the housing walls and stitch flange.

Final geometry

The charger (red), the PCB (orange), and the battery (blue) are packaged tightly in the housing. The bottom plate (purple) seals in the components with the help of a gasket, while offering improved aesthetics over a top cap.

With an eye towards mass-production, I modeled the housing with appropriate fillets, drafts, and parting lines for injection molding (above). The exploded rendering to the right shows all components as they assemble, including the plug and o-ring seal for the charging port. Mass-production versions would see the plug tethered to the housing with a flexible polypropylene hinge. 

Design Process – Overlay

Wishing to experiment with incorporating the turn signal elements into an exoskeleton that could be transferred between summer, winter, and fall/spring gloves, I worked to mount the housing and all electronics on an overlay that could be non-permanently affixed to any glove.

I settled on 6 LEDs per hand, all activated by touching the thumb and ring finger together. In this way, the two LEDs on the thumb are visible to oncoming traffic while the four on the index and middle fingers signal to vehicles behind.

I drew the overlay profile with Adobe Illustrator, laser cutting paper test pieces and checking lay-up on the glove between iterations. The final overlay was cut from elasticated fabric to allow it to stretch as the fingers curl around a handlebar

The final overlay incorporates heat-pressed reflective panels to further enhance visibility to motorists.

Heat-pressed TPU reinforcement was used to strengthen the housing stitch zone (bottom right) and to secure the conductive textile contact switches (top and far left).

Assembly Process

Beginning construction of the wiring harness, testing for fit along the way.

Complete electronics assembly, with the PCB to the left, the lithium polymer battery to the right, and the battery charger in the center.

All components secured within the housing with the battery charging. The housing illuminates green when charging is complete.

Two complete overlays with sealed housings and all wiring installed accordion-style to allow for stretch and compression as the fingers curl and extend.

Project conclusion

After securing the overlays to a pair of leather gloves with low-profile velcro to allow transfer between gloves, I rode them through a rainstorm and beyond. I experienced motorists giving me a safety bubble like they never had before, and found fellow bicycle commuters asking about them at stoplights. The videos below show what I now look like on my urban commutes.

These gloves dramatically increase my visibility to other motorists, and for the first time I can signal my intentions and feel confident they are being received and understood. Though many refinements to aesthetics and user experience are still necessary, these prototypes do at least satisfy my key requirements:

  • Waterproof: O-ring seals and gaskets in the housing ensure electrical systems are protected.
  • Front and rear visibility: LEDs on the thumb signal ahead; LEDs on the index and middle fingers signal behind.
  • Ease of operation: Textile contact switches require almost no pressure to activate (and make the gloves touch screen compatible).
  • Rechargeable: The battery can be charged through a waterproof micro-USB charging port without removal from the housing.
  • Battery life: The 150mAh battery powers all six 20mAh LEDs for over 2 hours at a 50% duty cycle. Under normal use conditions, the LEDs will only be active for ~5 minutes per commute (conservative estimate), or ~10 minutes per day, so one can expect a battery life of over two weeks.
  • Daytime visibility: The LEDs are really, really bright.

Next steps

  • After experimentation with velcro, magnets, and other temporary attachment mechanisms, I think fully integrated turn signals are the best option moving forward due to improvement in aesthetics, durability, and tactile feel/UX.
  • Electroluminescent wire should be explored as a flexible, conformable, visually striking alternative to individual LEDs.
  • Experiment with Bluetooth connectivity to pair gloves to additional, bicycle-mounted turn indicators.
  • Current battery life is more than necessary. Either the battery used should be smaller to reduce bulk, or more LEDs should be added to increase visibility.
  • Conductive thread should be explored as a method to replace conventional wires by stitching circuitry directly into the fabric. I would have to test for the likelihood of electrical shorts and shocks with this method, however.
  • Integrated circuits could be used instead of the PCB to reduce bulk. I went the PCB route for prototyping because I wanted the experience of making one.
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