Electric Chair – Prototype II Final Report: Electric Chair


Introduction:

At the meeting with CPRF residents on the beginning of the semester several residents requested safety lights on the back of their wheelchair. The lights would make them more visible at night to other vehicles. Also, some of the residents wanted headlights which would enable them to travel at night.  For the prototype II we installed LED lights and a headlight which can be controlled via wheelchair joystick. 

Description:

For the prototype II we acquired a wheelchair from CPRF. We bought 6 LED navigation lights and a low profile LED headlights. We connected the lights in 3 sets in series. Both lights and Arduino are individually fuse protected. The lighting system is powered by 24V just as the wheelchairs are. The system is controlled by the wheelchair joystick as shown in the attached joystick diagram. The wheelchair has to be in drive 4 in order to change the light  mode. The joystick operates on x and y voltage axis with 2.5 V being the neutral voltage on both axis. On the positive x and y axis voltage is increased to approximately 4.2 V, and on the negative side of each axis the voltage is reduced to approximately 0.8V. We chose the y axis to control the headlight and x axis to controller the navigation lights. Each set of lights is turned on when voltage exceeds 3.7 V and turn off when the voltage falls bellow 1V. This logic is implemented in the Arduino code which changes the light mode. The chair operator can switch drives to resume travel without the light mode changing. 

Arduino code

Diagrams:

 

Reflection:

Our project was to build the safety lights and headlights for the wheelchair. It’s something that’s already out there and that can be bought. We wanted to make it better looking but still effective. Instead of accessing the DX Bus system we decided to clone the joystick harness. LED lights and the headlight work fine and can be turned on and off with the wheelchair joystick.  

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