Part 1:

1. Applications of Pulse Width Modulation

Conduct research into applications of pulse width modulation (PWM). Include proper APA citation for all sources referenced.

Include the following:

• An explanation of how pulse width modulation allows analog results via digital control.
• Applications and uses of PWM in Arduino based systems
• Examples of the various methods to achieve PWM with the Arduino.
• How PWM is implemented with another processor such as the Intel i7.

Part 2:

• Merits of the Engineering Design Approach

Discuss the merits of the "engineering design approach" presented in this course and the risks associated with not following such a methodology.

Microprocessor Engineering Design Approach

There are many definitions of engineering, however to establish a baseline in our thinking we will consider the following definition:

Engineering: the application of science and mathematics by which the properties of matter and the sources of energy in nature are made useful to people. (Engineering, 2015)

It is important to consider this definition as a distinction from many other terms that are being used today by those that may be performing some level of "design" and utilize some of the same tools such as microcontrollers as you will as an engineer. Engineering is based upon a structured discipline and while creativity and innovation are very important elements, the utility and safety of modern designs depend upon the level to which the designer utilizes a disciplined engineering design approach.

As a contrast, an inventor or hobbyist may also create innovative designs; however the approach they take may or may not be structured. In fact, today you will even hear the term "hack" being used quite often by those who take original designs and repurpose them based to some extent on trial and error.

This innovation and experimentation should not be considered necessarily "bad" and indeed may even have its place. We will however, approach our work based upon the definition we presented at the beginning of this lecture.

We will approach engineering design from a system's perspective. That is, we will consider the desired inputs and outputs given any special conditions or states. There will also be a natural progression that involves the following steps:

1. Gather requirements in terms of desired inputs, outputs and states of the system to be designed.

2. Analysis will then be performed to establish the desired voltages, currents, power, input/output resistance, etc. To the extent possible, engineering calculations based upon circuit theory will be employed. This is where scientific and mathematical principles are utilized. From this analysis component selection can be made.

3. Gather information to understand the basic properties of components that will make up the design. This will consist mainly in acquiring the data sheets for each component used in the design.

4. Pseudo-code and/or flow chart is constructed to help guide the code development process.

5. Code Development and simulation will then be performed. For example there are Arduino simulator/emulators available to emulate Arduino code execution. Additionally, for purposes of simulating external circuitry being interfaced to the Arduino, National Instruments MultiSIM or similar circuit simulator can be used. This is a critical stage, as any deviations from theoretical engineering analysis and simulation must be understood prior to moving onto physical construction of the system.

6. Physical construction of the system involving the use of a breadboard and interfacing to the microcontroller. This is referred to as prototyping.

7. Testing will then be performed with specific test cases. Test cases are known inputs that result in expected outputs.

8. Conclusions are then drawn as to the relative success of the design based upon the established key performance indicators. Key performance indicators often align directly with the requirements but may also go further to involve other measurements to ensure the design meets quality and safety standards.

It is highly recommended and expected in this course and others to follow in your engineering studies that you take a similar approach to all of your design efforts. Thus, your approach should be methodical and based upon an understanding of not only what you are trying to accomplish in the design, but also an understanding of the inherent limitations and specifications of all of the components chosen. Failure to understand for example the current limitation on a microcontroller pin can not only result in improper functioning of the hardware but also damage to the component and depending upon the application , significant damage to property and or life.

Notice that entering code into an integrated development environment for upload to the microcontroller does not begin until midway through the design process. It is often tempting to start with a code editor as this part of the process is often considered the most interesting part for someone who enjoys programming. This could lead to a great deal of rework and possible damage to equipment.

A thorough understanding of the requirements, design success criteria, and hardware specifications are essential in microcontroller design engineering. The emphasis on hardware may be new to some who have worked previously only with programming high powered workstations in languages such as Java and C++.

Finally (and by no means least in importance!) a key goal in any engineering design is to ensure the system being designed is fail-safe. A fail-safe design is one in which failure of either software or hardware results in a predictable condition or "safe state". (Herena, 2011)

There will be more discussions of this very important topic throughout the course; however it is highly recommended that the reader visit the site referenced above for an enlightening and nontechnical discussion of fail-safe design.

Arduino Emulators:

• CodeBlocks - http://arduinodev.com/codeblocks/
• Simuino - https://code.google.com/p/simuino/

References

• Engineering. (2015). Merriam-Webster. Retrieved from http://www.merriam-webster.com/dictionary/engineering

• Herena, P. (2011, Feb. 23). The Principle of Fail-Safe. AIChEChEnected. Retrieved from http://www.aiche.org/chenected/2011/02/principle-fail-safe

Part 3:

Using PWM to light an LED

1. Lab 2a:

Procedure:

• Watch the video: Tutorial 02 for Arduino: Buttons, PWM, and Functions (https://www.youtube.com/watch?feature=player_embedded&v=_LCCGFSMOr4)

• Construct the breadboard circuit and implement the program presented in the video and in Chapter 2 (pp. 29-35) of your textbook to control the brightness of the external LED via PWM.

Lab 2b:

Procedure:

• Design a circuit and Arduino program that accomplishes the following:

o Reads a press of a pushbutton once, and it cycles through all possible brightness values

o A press of the pushbutton a second time during the cycle, and it will "reset" the system by turning the LED off and setting the brightness value back to 0

o Another press of the pushbutton again, and it will then start the brightness cycle over again

Include a video of your circuit in operation and any computer screenshots during its operation. Please include your Grantham ID number in the video to show your work.

Send your code file (.ino) of the lab completed and operational as well for credit.

Analysis/Discussion:

Explain the process you used in this lab to arrive at the final design of both the hardware portion and the software portion to achieve the design objectives.

This lab introduced interfacing an external LED and a pushbutton switch to the Arduino. Describe some practical considerations that must be taken into account when interfacing each of these devices in order to achieve desired operation and component protection.

PWM was used in this lab to "simulate" analog output from the Arduino. Measure the voltage associated with the minimum value of the analog output and the maximum value of the analog output. Take a picture of the measurements of the DMM display to confirm the voltages at analog output of 0, 127, and 255. What do you notice about these values regarding the relative brightness of the LED? Describe how the values that were assigned to the output to the LED establish the relative "brightness" of the LED.

As a design engineer, describe the method you would use to ensure that devices interfaced to a microprocessor can be done so safely. That is, how would you determine the limitations on the current that can either be sourced or sunk by a microprocessor? Provide sample data for both the Atmel ATMega328 and the Intel i7 microprocessors in terms of maximum current ratings per pin and total current limits for each microprocessor. Include your answers with your code, screenshots and readings submitted.