Introduction to the Microcontroller

MECH 452 - Mechatronics Engineering
Laboratory #1 – Introduction to the Microcontroller
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In this laboratory you will work with the USB-Boarduino microcontroller that uses the
ATmega328 microprocessor. The purpose of this laboratory is to introduce you to the
microcontroller and its programming language. Although written for students who have no
previous experience with the Arduino, it also provides a refresher on applied electric circuits.
Each group (of 2 students) will be required to submit a short group report.
Required Parts List:
• USB-Boarduino on a protoboard
• USB/mini firewire cable
• multimeter with leads
• assorted LED’s, resistors and wires
Figure 1. USB-Boarduino microcontroller (ATmega328 microprocessor).
Procedure for Laboratory:
1) The board has been prewired. Check that you can identify the components in Figure 2.
2) Log on to your computer as User = studiolab and Password = ilcp. Go to the Laboratories
page on the course website, select the file Lab Report Template and save it to your Group
directory with a different but descriptive filename. Take a moment to enter your group
number, names and the date on the template.
3) Go to Programs page, select MECH452introswitch and save it to your Group directory.
Open the saved program by double clicking the filename. You should get Figure 3.
USB
connection
Arduino
reset
button
proto-
boards
5v rail
pushbuttons
(specific to
this lab)
ground rail
5v regulator
(not used in
this lab)
Figure 2. Protoboard with USB-Boarduino and main components labeled.
(2013 draft)

Upload
button
Figure 3. Message when opening file for first time.
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4) Click OK, the folder MECH452introswitch will be automatically created and the Arduino
editor should open as in Figure 4. Note that the background in Figure 4 is white. If the
background is grey, it means you won’t be able to edit. To correct this, go to “File” in the
header, then “Preferences” and then untoggle “Use external editor”. The background
should switch from grey to white (and you will be able to edit and save).
5) Confirm that the pin assignments in Figure 4 are correct (by checking the actual location of
the wires relative to the Arduino pins identified in Figure 5).
Figure 4. Header for the MECH452introswitch program in the Arduino editor.
Figure 5. Pin assignments on the USB Boarduino.
Serial
monitor
button

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6) Use the USB cable to connect your computer to the Arduino. The green (or red) mini-LED to
the right of the USB connector on the stack should go steady on, indicating that that you are
receiving power. The red/green mini-LEDs to the left of the USB connector should flash,
indicating that communication is being tested.
7) Click on the arrow button in the header (labeled in Figure 4) to upload the program to the
Arduino. If you get the error message in Figure 6, you may need to use the Device Manager
on your computer to determine the number of the COM port that is actually in use.
Figure 6. Error message if wrong COM port.
8) Once the correct COM port is selected, you may get the error message “Wrong
microcontroller found”. To correct this error, go to “Tools” in the header, then “Board” and
make sure that “Arduino Duemilanove w/ATmega328” has been selected.
9) Once you have the correct COM port and the correct microcontroller selected, then when you
click on the arrow to upload, you should see the message “Compiling sketch” followed by
the message “Done Upload” at the bottom of the editor window. When the Upload is
complete, the Green LED on the protoboard should flash, indicating that the program is
waiting for a button push to start the program.
10) Click on the serial monitor button on the right side of the header (labeled in Figure 4). Note
that this resets the program (green LED stops flashing, mini-LED’s flash, then green LED
restarts). After the reset cycle is complete (wait for it, be patient), the “debug” window seen
in Figure 7 appears. This window will echo “Serial.println” commands and give feedback to
the user on program status. Make sure that the bottom of the window shows “9600 baud”.
11) Press the reset button on the Arduino (see Figure 2 for location). The message in Figure 7
will repeat itself to confirm the reset.
Figure 7. Serial monitor window.

12) The operation of the program should be as follows:
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• green LED on pin P3 flashes ON and OFF once program is loaded
• user presses Button on P9 (white button) to start program cycle
• green/yellow/red LED's on pins P5/P4/P3 flash ON and OFF sequentially
• user presses Button on P8 (red button) to stop program
• green/yellow LED pins P5/P4 flash ON and OFF together, red LED pin 3 solid ON
Pressing the reset button on the Stack will restart the program
13) Experiment with the program and the circuit, and answer the following questions:
a) Measure the voltage between the vertical rails on the protoboard and confirm that its
close to 5v. Note that this supply is taken from the Vcc and Gnd pins on Arduino.
b) For the Red LED circuit (the one connected to Pin 3):
i) Measure the voltage across the LED when it is solid ON (see Figure 9 for
recommended way, namely with jumper wires). Find a website reference that
confirms this is the expected voltage (and cite the address in your report).
ii) Measure the resistance of the 470 Ω resistor (see Figure 10 for recommended way).
Why is it important to remove the resistor before measuring ? (ie. what’s the point
that Figure 10 is trying to make?) Find a website reference that confirms the colour
coding and the tolerance for the resistor (cite address of website, report colour coding,
comment on whether within tolerance).
iii) Measure the voltage across the 470 Ω resistor, when the Red LED is solid ON.
Calculate the current with Ohm’s law and report the value.
iv) Measure the current when the Red LED is solid ON (see Figure 11 for recommended
way, namely move one of the LED leads to another row, and use jumpers on the
multimeter to complete the circuit). Does the measured current match that calculated
in the previous step ? Is it within measurement error ?
v) If the maximum recommended output for a pin is 20 mA, what is the smallest resistor
that the 470 Ω resistor could be replaced with, according to Ohm’s law? You can
assume the same voltage drop across the LED as measured in i) above. Find a
website reference that confirms (or not) the maximum output (and cite the address in
your report).
c) What is the purpose of the 470 Ω and 2 KΩ resistors in the circuit of Figure 8 ? Is there
any significance in the fact that they are different ?
d) Measure the resistance of the 2 KΩ resistor. Confirm that its value according to its
colour coding is not 2 KΩ (use website from c) above). Is this a problem ?
e) What happens if you reverse any of the LED's ? Why does this happen ?
f) Pins 8 and 9 are connected to the "low" (ground) side of the buttons. What happens if
they are connected to the "high" (5 v) side of the buttons ?
g) Make a copy of the program MECH452introswitch and rename it Group#introswitch
where # is your group number. Modify the program such that only one push button is
needed to start and stop. Don’t forget to put your names in the header of the modified
program. Run the program to confirm that it still works.

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14) To receive credit for this lab, you must demonstrate to the TA that your (one button) program
is operating correctly. Finally, you are encouraged to complete a draft of the report before
leaving the lab. Do not disassemble the circuit. You will need it for the next day (and for
subsequent labs).
Procedure for Tutorial:
The instructors have introduced 4 wiring errors to your circuit that you had working the day
before. Identify and correct the 4 errors and demonstrate to an instructor that the original
program.
Report (due before end of tutorial period)
You are required to submit your report as an Adobe (.pdf) file by email to
mech452.2013@gmail.com. Please use as the Adobe filename: “Lab1StampIntroGroupX”
where “X” is your group number and use the same name in the Subject line of your email. The
report must: a) Summary Section (what did you do and what did you learn ?), b) Answers
Section (answers to questions of Step 13) and c) Appendix Section (listing of
Group#introswitch, with additions or changes from original MECH452introswitch highlighted
(eg. by colouring changes in Word).
Marks will be deducted for the following format errors: a) incorrect filename, b) incorrect email
Subject, c) no student names in header of program listing.
GREEN
Pin 5 Pin 4 Pin 3
YELLOW
RED
RED RED
Figure 8. Circuits for Lab #1.
Pin 8 Pin 9

Figure 9. Measurement of voltage across Red LED.
Figure 10. Measurement of resistor resistance.
Figure 11. Measurement of current in Red LED circuit.
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