Microprocessor Systems Engineering – Week # 2 Lab 1

Using PWM to Light an LED

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.

Rules for lab submissions:

1. The lab document must be a Word document. PDF files are NOT accepted.

2. All screenshots must be included.

3. All Multisim screenshots must include the date/time stamp. See TOOLS AND TEMPLATES for the procedure to display the date and time.

4. Any and all Multisim files must be submitted.

5. Any equations used must be typed in Word. Copy and paste of equations from outside sources is prohibited.

6. No graphics are allowed in the Word document other than screenshots of circuits from Multisim and hardware if applicable, with the date/time stamp.

7. The lab template should be used. Specifically, it is brought to your attention that a summary MUST be provided explaining the results of the labs, the relationship of the results to expected results, and any challenges encountered.

8. Hardware portion of labs should include screenshots of the assembled circuit with your name and student GID number written on paper next to the circuit. There should be screenshots of the instrument readings with the date and time stamp on lower right corner clearly shown.

Any violation of the submission rules above will result in a grade of 1.

Grading Criteria	Maximum Points
Meets or exceeds established assignment criteria	40
Demonstrates an understanding of lesson concepts	20
Clearly presents well-reasoned ideas and concepts	30
Uses proper mechanics, punctuation, sentence structure, spelling and APA structure	10
Total	100