Explain why casing of devices is usually adviseable.

Executive Summary
Our project was based on the need for a low-cost Point of Care (POC) device in developing countries that can help deliver a quick diagnosis to lowering mortality rates and using already proven disk technologies. The project was facilitated by first setting up some key objectives. These objectives included spinning a test disk that houses the patients samples, at various revolutions per minute (RPM), heating the test disk to 60 degrees Celsius, including a light feature to read results and provide a diagnosis after test completion, and including all of the sensors that would complete this system. Our solution to these objectives is to have a variable speed motor to spin the test disk. A controller and coded program are then used to allow the motor to run at specific speeds for given periods of time. To satisfy the heating requirement, our device utilizes a ceramic heating element. This element is also connected to the controller which monitors the heat of the test disk using heat sensors. These sensors give the controller actual values of the temperature, which then turns the heating element on or off. Lastly, we would use an ultraviolet (UV) light to determine the result of a diagnostic test.

Price, efficiency, durability, and ease of use were the four main characteristics we used when evaluating our design. The most important characteristic for our design was the price point, because our device is to be utilized in developing countries. Accordingly, a simple compact design is paramount for ease of use; moreover, this design will be structurally sound to ensure durability as the device is designed to be used in remote locations. Efficiency is also important because getting results quickly allows diagnosis of these common diseases in a short amount of time, which will save lives and make treatment centers more efficient. The design of this project is meant for mass production, working with charitie to get as many units to countries in need as possible.

Design :

Point of care devices are mainly needed in AC power Source. Powered by an Arduino Uno and Parallax Semiconductor controller board, our device will deliver a fully autonomous solution that will be driven by a 12 volt DC motor with a max rpm of 3000 rpm. The motor which was chosen for use is a 12 volt Teac DC motor. This motor was initially used in reel to reel technologies. The speed of this motor is directly related to voltage change in the system. As very little torque is required to spin the disc there is very little power required to run this motor. In this design power distribution is important as the heat source will pull approximately 8 watts of energy.

During the development process we decided to replace our initial standard motor with a stepper motor. Our initial thought was that adding the stepping feature would allow for the clocking of the test disks during testing, so the detection chambers of the disk would be aligned with the UV light after the rotation phase of our program. However due to drastic changes that were required to be made in the Arduino library code for faster spin rates coupled with a larger power requirement of 19.2 Watts just in the motor design alone the team decided it would be more beneficial to use a conventional dc motor. In order to drive the motor we chose the Adafruit motor shield which attaches directly to the Arduino board itself. The shield itself will assist in a dual speed fully autonomous solution while using a ramp up and ramp down condition. This technology will aid in the delivery of the blood sample to the detection chambers.

During the rotation of the dc motor, a digital UV light will luminesce into the detector chamber. A sensor on the other side of the disk will then check the amount of light that shines through the fluid. The amount of light detected by the sensor will determine whether the test is positive or negative for a certain disease. To ensure that our disease detection is error proof, each detection chamber of the disk will be systematically numbered and the disk can only be installed one way. With the chambers numbered, the disk can have multiple types of diseases loaded at one time, and our program will be able to interpret the UV readings for each chamber independently.

To aid in the chemical reactions required for testing, our device requires a heat source that will reach and maintain a constant temperature of 60 degrees Celsius +/- 5 degrees Celsius. The heat source we initially chose was an optical heating based element. Due to the critical need for high temperature and low power consumption we had trouble finding an adequate optical heading based element, as there is currently nothing on the market that could meet our specific requirements. The heat source we decided to use instead is a 5V ceramic heating element that is made of a material that is similar to what is used for a hair straightener. This specific heating element can reach temperatures up to 80 degrees Celsius. A UV thermopile temperature sensor will be utilized to monitor and relay the actual temperature to the controller. The controller will then control the heating element to maintain the desired temperature of 60 degrees Celsius.

The casing of the device needed to have durability to withstand any extreme weather condition. Due to the desire to use these devices in developing countries, it is important that our design is able to maintain its structural integrity in extreme environments. Therefore, we have chosen to retrofit a standard 13.37”x 11.62”x 6” Pelican case. Once we received the storage case it was apparent that there was a need to procure a surface panel for our chassis. We were able to locate a surface panel from Data Pro. In Appendix A, Figure 4 the surface panel CAD drawing shows where the panel will be cut out. The surface panel is now retrofitted to hold and stabilize all of our hardware and controller components that are mounted to the back side of the panel. In Figure 5 and 6 shows our surface panel mounted with components.

To power our device we will utilize a 3.7V lithium ion battery pack which is powered by Adafruit’s Powerboost 1000 charging shield. Similar to a cell phone charger, our device can be powered by either AC or DC power.

In order to detect pass/fail results and device failure interruptions our initial design called for the use colored LED’s; however after further consideration we have chosen to use an LCD panel that will be located on the outside of the box. This LCD panel will utilize a screen to display any specific device failures that may occur during the test as well as the pass/fail results of the test.

As we develop our prototype, we have envisioned a few other design options to enhance our product that can be added once our current prototype is complete. Since our POC device will be used in remote locations, we chose to power our equipment with a DC battery. We would like to add a solar panel that could recharge the power source battery and allow our device to operate entirely off of the grid. The solar panel would be mounted to the top of the device which would make it vulnerable to damage. To ensure we keep our device durable, we could enclose the solar panel in a clear plastic protective container. We could also have the solar panel stored on the inside of the case, and allow for the solar panels to be removed from the case for charging in direct sunlight.

A second design enhancement would be altering how our device displays the results of the test. Our current proposed method is to have an UV light read the test disk with a detector on the back side of the disk. To aid in the result analysis, we could have the sensor send a signal to a cell phone, or other digital device, that would display the results in an electronic manor that could easily be transferred into patient or disease records. Having this feature could help doctors decipher the results more quickly, which would lead to a more timely diagnosis.

The final enhancement that could be incorporated into our design, is the ability to run multiple test samples at once. Adding more samples would take more power, as it would likely need another motor and more heating and lighting elements. But, allowing for the testing of multiple samples at once would could speed up diagnoses within a clinic. Since the current design would have to drastically change, this would require an extensive redesign and further testing.