 Mobile Desk Chair
Information and Data was submitted to Parallax by Devrin Talen:
I have been working for a little while on something I like to call the Mobile Desk Chair Project. In addition to what I explain here, there is also a blog updated and maintained by me, here, where I post the latest developments with the chair.
 Basically, my goal is to develop a mobile desk chair that researches alternate methods of user control and data presentation. I started with an old wheelchair that was generously donated by a friend at church. The wheelchair was still in fine working order. My first step was installing a new chair onto the wheelchair. I removed the stock chair and bolted on a desk chair that I purchased from Ikea. That phase complete, I still had in the proprietary control system.
 The next step (and hereafter) is where Parallax's Basic Stamps have been the key to enabling this project. I knew that I wanted to develop a novel way to control the chair, rather than just using the standard joystick interface (above). I eventually came up with the idea of using a glove that would measure the tilt of the driver's hand and use that information to infer which direction the driver wanted to go. To do that, I simply used the Memsic Accelerometer, which allowed me to easily measure the tilt of the glove. I mounted the accelerometer onto the glove, and it is read by a BASIC Stamp 1 Project Board mounted under the right armrest (right). The BS1 also mimics the glove's movements on a servo-controlled joystick, so the driver can see what they are doing with the glove (below).
 This data is sent via serial communication to a Board of Education with a BASIC Stamp 2sx, which then converts the data from a 2-axis coordinate system (with an x and y axis) into drive values for each of the two motors on the wheelchair. The BS2sx uses two digital potentiometers to control two speed controllers for the motors. The motors and speed controllers use a separate 24V power supply. Forward/reverse is accomplished by DPDT relays between the speed controllers and the motors.
I invite you to visit the Mobile Desk Chair blog for photos of the chair and of the various Parallax components, in addition to various practical hurdles I encounter and how I eventually deal with them. I continually update this blog with the latest developments in the chair.
Devrin Talen
Bethesda, MD
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