Kevin Hon, Joel Manansala, Adam Chodaba

HW5

Section 1

In Assignment 5, the work was divided by each member to research an aspect of the project to further our understanding of our device and provide extra details/ideas to it. Below is a small chart showing the breakdown of each member’s contribution to this assignment.

Kevin Hon / Joel Manansala / Adam Chodaba
Percentage of effort towards this assignment / 33% / 33 % / 33 %

Section 2

In the previous report, it was pointed out that some accessories that would be beneficial to add to the Watch Breathalyzer included things such as a GPS and an accelerometer, on top of the existing hardware needed to have a functioning breathalyzer. The accelerometer will be able to detect whether its user is accelerating at an unusual rate, and the GPS will be used to track the user in question (and confirm velocity) if it is determined that he or she is operating a motor vehicle. Of course, the user will not always be the one in control of a vehicle when it is detected that they are going above a certain speed. Therefore, an alert will be sent via text or email that the user is going above a certain speed, and allow that recipient to determine whether the user is driving or not. However, implementation of this sort of text/email alert system is out of scope for this section of this report. In this section, we will be focusing on the implementations of both accelerometer and GPS components of the product.

It was established in the previous report that the accelerometer that the team is going to use is based off piezoelectric principles, wherein electricity is produced when pressure is applied to a crystal. When an object accelerates, it can apply a pressure to this crystal, generating an electrical signal. The intensity of this signal can indicate how much acceleration the object is experiencing. There are some things to consider when trying to apply this principle to our product. One possible way to implement a piezoelectric accelerometer is to have a mechanical stack. This includes a base at the bottom, the crystal on top of it, and some sort of weight on top of that. This could be considered a rudimentary application, since the accelerometer would be only able to measure compressive forces.

Knowing this, there are different parameters that can be adjusted in order to get different results. The mass on top of the crystal can be increased to increase electrical signal output and sensitivity, and the number of crystals under the mass can be increased to increase the output. Doing either one of these will reduce the resonant frequency of the device and the noise level of the signal. Depending on what kind of CPU and logic circuitry is used to process the signal, these parameters may need to be adjusted accordingly. To take in to account acceleration in more than one direction, perhaps multiple masses can surround the crystal so that readings in multiple directions can be recognized.

One needs to also think of a practical GPS design for the watch as well. Typically, for stand- alone GPS receivers have a reference frequency (most likely the frequency at which the device checks for GPS signals from the satellites) of 16.36 MHz. However, our device is not a stand-alone receiver. The Watch Breathalyzer will also be doing other forms of wireless communication, such as sending out text and email alerts. Therefore, our device may require multiple reference frequencies, such as at 10MHz, 13MHz, 14.4MHz, 20MHz, and so on. Having our device utilize multiple GPS reference frequencies may result in a more complicated design or tax the system in question beyond what may be considered “healthy” operation.

In terms of designing a GPS receiver circuit, the team will most likely need a lot of parts, and time, (the circuit may become a little complex). Such things we may need include RF bandpass filters, DC antenna supplies, SAW filters, microprocessors, crystal based Real-Time-Clocks, EPROMs, oscillators, and more. It may be that we can utilize some of the microcontroller board that was mentioned in the previous report to conserve space and reduce complexity, though this may put extra strain on the microcontroller. With extra strain, comes extra heat, which would not be welcome in a device such as this. Extra heat would mean an uncomfortable user experience, and the user will be less inclined to use our product.

Judging by the popularity of similar electronic projects involving sensors and displays using an Arduino board along with the vast amount of documentation and guides for those microcontrollers, it seems like a good fit for the project. The board will be selected based on size, voltage requirements and functionality. The board will connect the various inputs and output devices of the product such as the buttons, LED, speaker, sensor and screen. The Arduino language is based on C/C++ and is very easy to program with and access sensor inputs as well as outputs. The microcontroller will be programmed to display the time as well as the results of the Breathalyzer test when the test results are available. There are many guides online to assist with learning the programming that are available if necessary. The board supports both analog and digital sensors and can be connected to a Liquid Crystal Display to show output.

The economic constraints of the project are mainly the cost of the various components including the case, microcontroller, battery, display, buttons, and sensors. The economic constraints are crucial to be able to sell the product at an affordable price and still make a profit. The environmental constraints of the project are to avoid the use of environmentally toxic elements such as lead or mercury in the product as well as the ability to easily recycle the components if it is feasible to ensure. The health and safety requirements are that the device should not release harmful levels for radiation or heat and should not contain a battery that has a risk of exploding. The device should also not contain sharp or rough edges to avoid damaging the skin of the user. The device shall have easy manufacturability by consist of a handful of off-the-shelf components that can be assembled and programmed to create the finished product. The only component required to be designed will most likely be the case for the product. The sustainability of the product will require the battery to be rechargeable and last long before it fails. The sustainability of the product also requires that the case and screen can survive the wear and tear that a watch or similar device worn on the body undergoes during usage. It is the professional and ethical responsibility of the device to output accurate readings of the BAC of the user. An inaccurate reading can cause the user to make a bad decision such as driving when the device incorrectly outputs a reading lower than the maximum BAC for driving which can have legal consequences.

Objectives and Attributes

Safe

Well-Constructed

Looks Cool

Accurate Readings

Environmentally Safe

Small form factor

Low Voltage requirement

Good Battery Life

Low Heat Generation

Good Screen Visibility

Responsive Interface

Intuitive Interface

Resists Range of Temperatures

Water Resistant

No Sharp Edges

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