About the Project

Introduction

A healthy human is able to maintain a constant body temperature of 98.6°F (37°C) despite the temperature of the environment. In a hot environment, the body sends a signal to the brain via the spinal cord to say the body is overheating; the brain then sends a signal back down the spinal cord and tells the body to cool itself by perspiration. Many people with spinal cord injuries, however, are unable to complete this operation. With the loss of the ability to sweat, a person needs a careful control of his or her environmental conditions or their body temperature will begin to rise excessively. Likewise in a cold environment, the body may not be able to get the messages through to the brain that the body is cooling down, and if left untreated, the person will soon become hypothermic.

There are a variety of clothing products designed to heat or cool individuals in order to regulate body temperature. Some heating garments use a heat source connected to stationary equipment, with a heating system attached to the clothing. Due to the high power requirements, the battery power needed for this type of system is either very bulky (lead acid) or prohibitively expensive (lithium-ion), resulting in very limited mobility because of the electrical connections. Cooling vests use ice water that is pumped from a reservoir and gets circulated throughout the vest.

These designs, aimed at those working or living in harsh environments, often are not intended for those with medical conditions, such as quadriplegia. Those that are available have downfalls including limited mobility and safety issues. A project was started last semester to rectify this.

Background

The goal of this project is to modify a heating/cooling system for the use of quadriplegic wearers. Last semester, in combined effort with the MSU Center for Persons with Disabilities, a jacket was designed to control the temperature of an individual by heating or cooling water and sending it through a network of tubes lining the jacket. The system attaches directly to, and is powered by, the users’ wheelchair. When activated, it pumps heated (or cooled) water though medical grade tubing in the jacket, this in turn influences the temperature of the wearer. There are limitations in the design that must be addressed to complete this project.

Safety is the most important factor to consider when designing this vest. In the current design the system used water that is pumped though a hose system. A temperature regulator was not implemented, which could cause serious injury if the water surpasses a safe temperature. Therefore, the water temperature must be monitored by the system to ensure that the vest does not get too hot. If the controller reads a temperature that is potentially dangerous a signal will be sent to shut the entire system off.

Power conservation is another issue from the original design. The system could not hold an automated setting because of the extensive power that was drawn from the wheelchair’s battery. Since the system is drawing power from the battery of the wheelchair, as much energy should be utilized as possible to prevent too much power loss to the chair. A voltage divider will be used to provide an appropriate voltage level to all the major components of the system including the microcontroller.

In order for this design to be truly effective it must be easy for the customer to use. In phase I of the project there was a limited user control. The only settings were off, heating and cooling. The switches for these settings were not accessible and were limited in range of operation. Our task is to develop an automated system that will detect the user’s body temperature and adjust the temperature of the jacket according to his needs. In addition to that, the control of this system will be within reach of the user. Manual, automatic, and off will be the type of options available. While operating in the manual condition, the user will be able to select from a range of temperatures that will allow for maximum comfort.