Lecture #1
EGR 262 – Fundamental Circuits Lab
EGR 262
Fundamental Circuits Lab
Presentation for Lab #1
Instructor: Paul Gordy
Office: H-115
Phone: 822-7175
Email: PGordy@tcc.edu
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Sequence of Electrical/Computer Engineering Courses at TCC
EGR 260 (3 cr)
Circuit Analysis
ODU equiv: ECE 201
Offered: F, Sp, Su
EGR 261 (3 cr)
Signals & Systems
ODU equiv: ECE 202
Offered: F, Sp
EGR 262 (2 cr)
Fund. Circuits Lab
ODU equiv: ECE 287
Offered: F, Sp, Su
EGR 267 (3 cr)
EGR Analysis Tools
ODU equiv: ECE 200
Offered: F, Sp ?
EGR 125 (4 cr)
Into to EGR Methods (C++)
ODU equiv: CS150
Offered: F, Sp, Su
EGR 270 (4 cr)
Fund. Of Computer EGR
ODU equiv: ECE 241
Offered: F, Sp, Su
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Focus of EGR 262
EGR 262 is a unique lab course that was first developed at Notre Dame. It was
then adapted for use at ODU and then at TCC. The lab involves a combination of
hardware and software as various experiments are conducted by writing C
programs to use a microprocessor to control various types of circuits.
24k
18k
1.1V
3
+
V+
OUT
7
U1
OS2
-5V
1
6 Vo 1
2
-
5
OS1
OUT
3
+
7
U2
0
5V
4
OS1
V-
-
3k
V+
4
5V
V-
2
0
OS2
1
Vo 2
6
5
-5V
4.5k
3k
ICC11
C Compiler
27k
0
0
MicroStamp11
Microprocessor
Circuit
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Lab Topics/Lectures
EGR 262 introduces many topics that will be unfamiliar to the student. These topics
will be introduced in a lecture (or recitation) associated with the lab. Background
material is provided in the lab manual and the instructor will lecture each week on
topics to be covered the following week.
Lab/lecture topics include:
• Report writing (lab notebooks)
• C programming (similar to C++)
• MicroStamp 11 architecture
• Lab test equipment
• New circuit devices (LED’s, comparators, diodes, etc)
• New circuit applications (digital-to-analog conversion, analog-to-digital
conversion, power supplies, pulse-width modulation, etc)
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Lab Notebooks
Why use a lab notebook? Lab notebooks
are commonly used by engineers. When
I was a graduate research assistant, my
advisor required me to keep a lab
notebook where I would document the
work that I was doing. I would record
every modification that I made to a
program or a circuit. I would record
explanations of tests being run and the
results, even if they were not successful.
On many occasions, I found myself
looking into my notebook to find out
what I had done weeks or months before.
We tend to think that we will remember
modifications that we tried or the results
of tests, but they are easily forgotten.
My lab notebook became a valuable
resource.
Each student is required to have the
lab notebook shown (with 100
carbonless duplicates). They are
available in the TCC Bookstore.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
The following is part of a presentation made at Notre Dame on the lab notebooks
required for their EE 224 course (from which this course is adapted)
Engineering Lab Notebooks
A “must have” Skill
Note Dame
Presentation
Why Keep a Lab Notebook?
•
•
•
•
•
•
It is a “must have” skill for an engineer
Permanent record of work (diary)
Can refer to so you won’t keep reinventing the wheel
CAN reinvent the wheel if need be
Can be admitted as evidence in patent applications, lawsuits, etc.
Goal is to create a record so someone else can recreate your work. (don’t need to recopy instructions…summarize and include references.)
• May not seem important now, but it can help you in future labs (having a reference in
hand). And will develop skills that can be carried on to future courses and eventually
to the work place.
• Notebook is bound and pages are numbered for a reason. Pages can not be added.
And if pages are removed, it is obvious. If you mess up a page…draw a “X” though
it and go to the next page, don’t remove it!
• Date each page.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Note Dame
What to write in my Lab book?
Presentation
• EVERYTHING!
• Details, details, details!
• You never know what piece of information will help in the future.
• Equipment IDs, bench numbers, time of day, environmental conditions,
etc….
• Use the grading sheets as a guide for the minimum requirements.
• Your being graded on content, not neatness or grammar.
• But it does have to be legible and in English! (and it needs to make sense!)
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Lecture #1
EGR 262 – Fundamental Circuits Lab
What is in a Lab Report?
Note Dame
Presentation
Pre-Lab Section
• If you make calculations…write them down
• Schematics
• Breadboard layout plan
• Can print program listings and tape in book
• Make sure you include in your white copy also
IN-Lab Section
• Keep a “diary”
• Write down your problems, tasks, data, results
• If you make a change in the schematic, make a note of it.
• Keep a revision trail of your code. Note problems and fixes.
Post-Lab Section
• Create your graphs and tables (can paste in)
• Summarize your findings, analyze them.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Note Dame
Presentation
Notes:
• Program listings….include pre-lab version and then final version. Discuss
all transitional programs and issues.
• Making note of every minor schematic change will enable easy
backtracking if you went down the wrong road to try and solve a problem.
Trust me, you won’t always remember what you changed or what you have
already tried.
• When changing a program… save the new one as rev a, rev b and so on…
this allows you to go back if need be… It also will help in lab write ups to
refer to rev c changed this and that and fixed problem x.
• Breadboard layout diagram on course website.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Typed vs. Handwritten
Note Dame
Presentation
• Questions about what is acceptable.
• All typed is NOT acceptable.
• Must have proof that you are keeping a proper record of your work.
• Must take data somewhere, so make it in your lab book.
• Writing typed formal reports are important.
• Lab notebooks should be an important tool in creating them.
• Learn the basics first…walk then run.
• To summarize….we want you to learn how to keep a proper Lab notebook.
So we must have proof that you are doing that. That is why you were
required to use the carbon copy type books that you are using. In “real life”
you are going to be taking notes and keeping a record of your work. 9 times
out of 10 those notes are going to be hand written. Then these handwritten
notes will be used to create formal reports or presentations.
• An engineer needs to be able to convey his or her findings, ideas,
discoveries…and to be able to recreate what they have accomplished. Being
able to keep a proper lab notebook is a key cornerstone in your future as an
engineer.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Lab Equipment
Before beginning Lab #1 next week, let’s take some time to become familiar with some of
the equipment in the lab. Manuals are available online for more detailed information.
Agilent 34401 Multimeter
Use to measure voltage, current,
resistance, frequency, and more.
PS280 DC Power Supply
Two 0-30V variable supplies and one
fixed 5V supply.
Breadboard
Circuits will be constructed
on solderless breadboards
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Agilent 34401 Multimeter
Each workstation has two
Agilent multimeters. We will
use these meters to measure:
1) Voltage
2) Current
3) Resistance
Note the location of the test
leads as well as the buttons that
are pushed for each type of
measurement.
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Note: The two leftmost leads
can be omitted in many cases.
Lecture #1
EGR 262 – Fundamental Circuits Lab
Agilent 34401 Multimeter
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Lecture #1
EGR 262 – Fundamental Circuits Lab
PS280 DC Power Supply
The DC power supply used in lab has two variable supplies and one fixed 5V supply.
0-30V
0-30V
5V
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Breadboard
SK-10 Solderless Breadboard (or equivalent)
A
B
Internal Connections on the SK-10 Solderless Breadboard
Notes: 1) Lines indicate which holes are connected under the breadboard.
2) To connect two or more wires together, plug them in the same row of holes.
3) Holes A and B are connected on some breadboards (as well as the similar holes on
the other horizontal rows).
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Example: Connect the following circuit using the SK-10 solderless breadboard.
5.6 kW
10 V
+
_
3.3 kW
1.0 kW
2.2 kW
1.5 kW
Connections to
10 V power supply
Jumper
+
_
Jumper
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Resistor Color Code
The resistance of carbon resistors is indicated by colored bands on the resistor. The first three
bands (A,B,C) indicate the value of the resistance and the last band (D) indicates the tolerance.
Values for Bands
A, B, and C
R is calculate using:
ABCD
R = AB x 10C
or
A = First Digit
B = Second Digit
C = Number of Zeros
D = Tolerance Code
Values for Band D
Gold – 5% tolerance
Silver – 10% tolerance
None – 20% tolerance
Examples:
Yellow, Violet, Brown, Silver: R = 47 x 101 = 470 W, 10% tolerance
Brown, Black, Orange, Gold: R = 10 x 103 = 10 kW, 5% tolerance
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Resistor Color Code – Carbon resistors
typically have 4 color bands that indicate
their value and tolerance. You can
determine the value of resistance and
tolerance using the handy online Resistor
Color Code Calculator shown to the
right. It is available at:
www.electrician.com/resist_calc/
resist_calc.htm
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Potentiometers
Three styles of potentiometers are shown below. The center lead in each style is
referred to as the “wiper.” Potentiometers are also sometimes called “pots” or “trim
pots.”
turn slot or wheel to adjust
turn knob
to adjust
turn to adjust
wiper
wiper
wiper
Potentiometer symbols
wiper
Note: If a potentiometers is used as an adjustable
resistor, use the center lead (wiper) and either side lead.
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Lecture #1
EGR 262 – Fundamental Circuits Lab
Diode
A diode is a semiconductor device that acts somewhat like a voltage controlled
switch. The symbol for a diode is shown below. The positive terminal of the
diode is called the anode and the negative terminal is the cathode.
anode
cathode
+
V
_
Diode Symbol
Diode Picture
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Lecture #1
EGR 262 – Fundamental Circuits Lab
LED (Light emitting diode)
LED’s are diodes that emit light when they are forward biased (a positive voltage
placed across the LED from anode to cathode as in Figures 2A and 2B). The
amount of light produced is proportional to the current through the LED
The resistance of an LED is sufficiently low such that if a few volts is
placed directly across an LED, it will be destroyed. Therefore, a current-limiting
resistor should always be used with an LED. The resistor must be chosen to yield
a current such that an appropriate brightness is obtained.
Luminous
intensity
anode
destruction
cathode
+
V
_
Figure 2A: Forward-biased LED
anode
(long)
cathode
(short)
Figure 2B: Physical appearance
I (mA)
12
20
Figure 2C:Typical LED characteristics
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Figure 2D: Pictures of LEDs
Lecture #1
EGR 262 – Fundamental Circuits Lab
Adjusting the brightness of an LED
In the circuit shown below, a potentiometer (adjustable resistor) can be varied to
control the amount of current through the LED (and thus control its brightness).
Current-limiting R
V
+
_
LED
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Lecture #1 EGR 262 – Fundamental Circuits Lab
Diode Characteristics
Diodes act somewhat like voltage-controlled switches where:
• The switch is closed when a positive voltage is placed across the diode
• The switch is open when a negative voltage is placed across the diode
The characteristics of an ideal diode are shown below:
Ideal Diode Characteristics
I
Forward biased diode
- diode acts like a short
(OV, any current)
V
Reverse biased diode
- diode is an open
(OA, any voltage < 0)
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Lecture #1 EGR 262 – Fundamental Circuits Lab
Actual Diode Characteristics
Actual diodes typically require a small amount of voltage before they act
essentially like closed switches (short circuits). Additionally, the relationship
between I and V diodes in the forward biased region is exponential and can be
described by the Shockley Diode equation.
Shockley diode equation :
Actual Diode Characteristics
I
qV
 nkT

I  I o  e  1


Vo is typically
0.6 – 0.7V for many
diodes, but may be
higher for an LED
Breakdown
region
Vo
Reverse biased
region (open)
Forward biased
region (approx. short)
V
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Lecture #1 EGR 262 – Fundamental Circuits Lab
Diode Modeling
Diodes models are often used to analyze circuits containing diodes. Diode models will
be covered more extensively in later courses, but three diode models are presented
below. Which model most closely represents an actual diode’s characteristics?
Model 1: Ideal Diode
I
Model 2: Ideal Diode
and voltage source
I
Model 3: Ideal Diode,
voltage source, resistor
I
Slope =
1/Ro
V
V
V
Ideal
Vo
Ideal
Actual
+Vo
Vo
+Ideal
Vo
Ro
(Replace the actual diode by a model
when analyzing a diode circuit.
Lecture #1 EGR 262 – Fundamental Circuits Lab
Analyzing a Diode Circuit
A circuit with a diode can be analyzed by replacing the diode with an appropriate
model (if the diode is in the correct region of operation).
For the example below, determine the current through the LED if a model for the
LED is used with Vo = 1V and Ro = 100 ohms.
I
500 Ω
5V
+
_
LED
LED model values to
be used for Lab #1:
Vo = __________
Ro = __________
Lecture #1 EGR 262 – Fundamental Circuits Lab
Tables in Lab Reports
Most lab reports will require tables. All tables should be created using good style to
create a professional appearance. Good tables should include:
• Grid lines
• Centered columns
• An appropriate number of digits (3 significant digits in most cases and often
maintain a certain number of digits after the decimal point)
• Column headings with variable name, variable symbol, and units
• Sample formulas for any calculations
Example: Poorly formatted table
voltage
current
power
Example: Nicely formatted table
Voltage, V (V)
Current, I (mA)
Power, P (mW)
0
1.21
0.00000000
0.00
1.21
0.00
1.25
2.45
3.06250000
1.25
2.45
3.06
2.5
3.69
9.22500000
2.50
3.69
9.23
3.75
4.93
18.48750000
3.75
4.93
18.49
5
6.17
30.85000000
5.00
6.17
30.85
6.25
7.41
46.31
6.25
7.41
46.31250000
7.50
8.65
64.88
7.5
8.65
64.87500000
8.75
9.89
86.54
8.75
9.89
86.53750000
10.00
11.13
111.30
10
11.13
111.30000000
Sample Calulation:
Cell C4:
=A4*B4
Lecture #1 EGR 262 – Fundamental Circuits Lab
Graphs in Lab Reports
Many lab reports will require graphs. All graphs should be created using good style
to create a professional appearance. Good graphs should include:
• Grid lines
• Appropriate titles
• Correct graph type – typically use x-y scatter graphs in Excel, NOT line graphs
• Axes labeled with variable name, variable symbol, and units
• Legend for multiple curves
• Show points and lines for measured data. Show lines only for theoretical curves.
Example: Poorly formatted graph
Example: Nicely formatted graph
Diode Current versus Resistance
30
30
25
20
15
measured current, I
(mA)
10
theoretical current, I
(mA)
Current (mA)
25
20
15
measured current, I
(mA)
10
theoretical current, I
(mA)
5
5
0
9500
8500
7500
6500
5500
4500
3500
2500
1500
0
500
0
Note that the x-axis values are unscaled. Avoid line graphs!
0
2000 4000 6000 8000 10000
Resistance, R (ohms)
X-Y scatter graphs are properly scaled.
Recall that each lab has Pre-Lab Tasks, In-Lab Tasks, and Post-Lab Tasks. The
following tasks for Lab #1 are from the lab manual. You should complete the Pre-Lab
tasks before our next lab meeting.
4.1. Pre-lab Tasks: Consider the circuit shown in Figure 15. This circuit
consists of a 5 volt independent voltage source driving a resistive circuit with a
single LED. One of the resistors is a 100 ohm resistor. The other resistor is a
variable resistor whose value can be changed between 0 and 5 kΩ. Since the
second resistor’s value is variable, the second resistor’s value is denoted by the
variable R.
Before coming to the lab you should do the following:
(1) Draw a labeled schematic diagram of the circuit.
(2) Include an explanation of how the circuit works.
(3) Draw a picture showing how you plan to breadboard the circuit.
(4) Draw a labeled schematic diagram with the diode replaced by a diode
model (use the values of Vo and Ro suggested by the instructor).
(5) Derive an expression for the current going through the diode as a function
of the variable resistance, R (using the diode model).
(6) Plot the current through the LED as a function of the variable resistance R
for at least 10 values of R from 0 to 5000 ohms. Use Excel or MATLAB
for all graphs in this course. Graphs must always be properly formatted.
Include both the table of values used and the graph in your notebook.
Always include sample formulas with tables of calculations in Excel.