Tetra Society Brief: New automated light for wheelchairs

Eric Molendyk using two early prototypes of the TetraLite.

Sometimes the inspiration for a design comes from a very unexpected place. Eric Molendyk is the Chapter Coordinator of the Tetra Society of North America, a non-profit organization that recruits skilled volunteers to create customized assistive devices for people with physical disabilities. Mr. Molendyk was hit by a car two years ago while crossing the street in his wheelchair. People travelling using wheelchairs are often less visible to drivers than pedestrians; the accident was the impetus for Mr. Molendyk to work with other members of the Tetra Society to build a lighting system for wheelchairs to make them safer on the street. The initial design was created by Brian Johnson, one of the volunteer engineers at the Tetra Society.

The TetraLite was very popular with the Society’s clients so they wanted to improve the design by automating the functions of the light and incorporating an independent power supply. Automating the light enables people with varying levels of mobility to use it. The automation needed to be controlled either by hand switches or through a sip and puff controller to allow people to access the function of the light with their breath. Powering the light from its own battery rather than the wheelchair’s power supply would enable the light be used on manually powered chairs or walkers.

There were a number of challenges for the design. The light had to be stable and waterproof to survive a Vancouver rainy day and couldn’t disrupt any other function of the wheelchair. As no two wheelchairs are exactly alike once they have been customized for the owner, the mount for the light had to be flexible and easy to attach without the use of tools. Price and the accessibility of parts for manufacture were also factors that the designers must consider.

Mr. Molendyk, as a user of the TetraLite, had important insights for how to improve the design. He explained to the capstone team that it is important for the light to retract away from the face of the person in the chair in social settings. When the light is near the face it is distracting and makes conversation more difficult.

The capstone team that chose to work on this project (Emily Beatty, Derek Graebel, Lester Lao, and Nikola Rajic) managed to make all of these improvements on the TetraLite and more. The team accomplished a number of these enhancements by making their design wireless. The wireless version is less susceptible to wear and tear, and easier ot install. The team also sourced an independent power source for the light, making it completely self–contained and even easier to install.

Capstone prototype for new TetraLiteThe team skillfully used a number of design strategies. In some cases they made use of existing parts such as the lights the Tetra Society already had on-hand. Other components, such as the circuit board, telescoping mechanism, and mount were designed from the ground up. The team’s prototype can be seen in the image on the right.

After meeting all the requirements of the Tetra Society’s proposal, this capstone team saw a number ways they could continue to improve the design. The team developed an iPhone app to control the light remotely. Being able to put the controls of the light in a pocket or backpack was useful, and the team could start considering other functions they could provide through the app such as GPS location for emergency situations.

The team values their capstone work, “This project has allows us to work with a client on a personal basis. It gives us the chance to get one-on-one interaction and design something that has purpose. Our design is going to be low power, low cost, safe, easy to assemble and install, and efficient.”

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