User:Medelen8/ENES100/BioVest Design D

Problem Statement
The purpose of this project was to design a device that measures ones vitals and is both as light weight and comfortable. Also the device must be easy to use and accurate within 3%.

Requirements for each element or component derived from system level goals and requirements
The final design has to be portable, lightweight, and accurate. Components involved include the shirt and whatever devices are used to take vitals, currently the only operational component is the thermistor which calculates body temperature (needs to be hooked up to an arduino micro to be put onto the shirt).

Vitals to be measured:


 * Measure pulse rate within 2%
 * Monitor respiratory rate within 5%
 * Measure oxygen saturation using pulse oxymetry with a 95% accuracy
 * Emit a light or sound warning when vitals are at abnormal levels
 * Weigh less than 2.5lbs
 * Insulation to maintain circuitry

Alternatives in design
We had several ideas before we started moving forward with the project. The first one being deciding on a fitted under armor shirt (or something similar) or a vest. The next one being deciding on a vital sign to measure At first we were going to do heart rate, but ran into problems with the device we wanted being sold out and taking too long to ship here. It was also more expensive than we would have liked it to be. We decided to use something more practical and readily available. We changed the vital sign we wanted to measure to body temperature and used a device called a thermistor. A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. Since the resistance varies depending on the temperature we could take that information and convert it into degrees in Fahrenheit which is exactly what we needed-- cheap, readily available, and fairly easy.

Initial Design
At first, we were going to prototype using a white under armor shirt. However the it was realized that said shirt may not fit all people (important for doing testing and presentations) so then we brainstormed and thought perhaps a vest would be a good idea. For testing purposes, it would not have to be anything fitted or fancy just something that could be adjusted(ie; construction vest) that could probably be picked up at a thrift store. Out first design included using a device called a Chest Strap. There were many to choose from but after creating a decision matrix we decided on the Trekmate Heart Rate Monitor. Future groups may consider looking into this as an option for furthering the project. The problem with this was that it was currently out of stock and we did not have time to wait for shipping.

Experimental prototypes and testing conducted during design
Since we decided to go with a thermistor for this cycle of the project we had to figure out how to hook it up and get it working. We began by reading the resistance on the thermistor, picked up an arduino uno, 3 wires, a USB cable and a 10K Resistor. After some research we found a code that used the Steinhart Equation which takes the resistance and voltage from the resistor and converts it to degrees in Fahrenheit (more information on this can be found in the Utilization of Knowledge in Design section of this report) after a few rounds of testing we fixed some minor errors including reading the wrong pin and changing the numbers in the code that calculate the temperature in Fahrenheit after calibrating the thermistor with a thermocouple, a device that already gives you the temperature in Celsius and varies on its surroundings or whether or not something is touching it. The following set up (pictured below) and code can be used to display the data on the serial monitor:

Appropriate optimization in the presence of constraints
We ran into the problem of a device we wanted being sold out and taking too long to ship to we adjusted our plan and decided to measure body temperature instead using a thermistor and other resources that were readily available (arduino uno, breadboard, wires, resistors, etc.) We also ran into the problem of being short one group member through the whole project, though we wasted a week investigating the possibility of the chest strap and counting on said MIA group member to complete tasks we made up for it by making the thermistor operational after calibration with the thermocouple and with the code and set up above.

Iteration until convergence
We had two possibilities for the design and picked the second one. 1) Chest Strap Device: Did not choose this one because item was out of stock, too long for shipping, information could not be added to application on smart phone-- vitals would have had to be displayed in too many different places. This design was simply too complicated and took too much time. 2) Thermistor with Arduino Code: We chose this one because you can add the the arduino code (when adding other vitals to this project), it was readily available so we did not have to wait for shipping, it was fairly easy to set up and calibrate, and can easily be hooked up to arduino micro to be sewn into a shirt when the project is at that point in development.

The final design
Our final design of our project cycle includes using a 10KOHM thermistor, 10K Resistor, 3 wires, an arduino UNO, a breadboard, a USB Cable, and a code that calculates degrees in Fahrenheit using the resistance and voltage change from the thermistor and 10K resistor (pictured above) the final code is below:

Technical and scientific knowledge
In order to complete this project, it is very useful to have basic knowledge of Arduino and circuits. We decided to use Arduino because it is readily available and because of time constraints, it was better than waiting for parts to arrive before working on the BioVest. Regarding the attachment of the devices to the shirt, it helps to be competent in sewing fabric together. In order to keep the devices or sensors safe from any damage, they have to be sewn into the shirt with fabric between the device and user. Regarding the code used for the thermistor, one must be familiar with the Steinhart equation. This is the equation in the code that is used to convert the resistance between the thermistor and resistor into a temperature. To make sure the thermistor was outputting the correct temperature reading, we used a Thermocuple with a Vernier LabQuest interface to calibrate it. We used the Thermocuple to test body and room temperatures. We then worked on the Arduino code for the thermistor to ensure that it would output the same temperatures as the Thermocuple.

Creativity, problem solving, and group decision-making
In order to come up with a solution, we thought about several possible approaches to completing the Biovest. Because there are so many options to get the measurements we needed, we created a decision matrix (pictured above) to determine which option was best for us.

Prior work in the field, standardization and reuse of designs (including reverse engineering and redesign)
Projects similar to the BioVest have been completed in the past. Examples include Under Armour's Armour 39, and OMsignal's Smart Shirt. We used these projects to get some general ideas for what we wanted to do with the BioVest.