Experiments in Electrical Engineering
Second Edition
To accompany S.A.Reza Zekavat’s
Electrical Engineering, First Edition
Ralph Tanner, Ph.D., PE, PRP
Western Michigan University
Contents
Preface...................................................................................................................................... iii
Lab 1: Instrument Familiarization ............................................................................................ 4
Lab 2: Transformers and Impedance Matching ...................................................................... 11
Lab 3: Balanced Three-Phase Circuits .................................................................................... 15
Lab 4: Ideal Amplifier Circuits ............................................................................................... 20
Lab 5: Frequency Response of a Passive Network ................................................................. 25
Lab 6: Operational Amplifier Circuits .................................................................................... 28
Lab 7: Rectifiers and Capacitor Filters ................................................................................... 32
Lab 8: Regulators and the Zener Diode .................................................................................. 38
Lab 9: BJT Switching ............................................................................................................. 42
Lab 10: Combinational Logic ................................................................................................. 47
Lab 11: Sequential Logic ........................................................................................................ 51
Lab 12: Load Test of AC Induction Motors ........................................................................... 55
Appendix A - Laboratory Safety............................................................................................. 58
Appendix B - Resistor Color Codes........................................................................................ 60
Preface
This lab manual was written to accompany the text, Electrical Engineering (1st ed) by
S.A. Reza Zekavat (Pearson, New York, 2013). It was written with a target audience of
engineering students who are majoring in a curriculum other than electrical engineering for
the Machines and Electronic Circuits course (ECE 2110) at Western Michigan University.
The course is conducted over fourteen weeks. No lab is held during the first week of
classes. The twelve labs will be conducted over the remaining thirteen weeks with room
allowed for such events as Thanksgiving break, or MLK Day. The lab instructor also has the
discretion to use the extra week to conduct make-up labs – should this be required.
In addition to appendices on lab safety and resistor color codes, this lab manual has
an appendix which attempts to illustrate the expectation the instructor will have of the
students as they complete their lab notebooks.
Lab 1: Instrument Familiarization
Learning Objectives:
1. Learn to wire circuits using a prototype breadboard.
2. Learn to use an oscilloscope to measure DC and AC voltages.
3. Learn to use a DVM to measure DC and AC voltages.
4. Observe the output of a function generator.
5. Observe the effect of source impedance on delivered voltage
6. Observe the effect of input impedance on voltage measurements.
Introduction
The effective use of instruments to take measurements is vital to success in working
with electronic circuits. This laboratory will give the student the opportunity to create
several circuits using the prototype breadboard and then obtain measurements of the circuit
values using different input sources and measuring devices.
A major goal of this lab is to help provide the student with a better understanding of
the appropriate uses of these tools for future labs.
The prototype breadboard provides a
platform upon which components can easily be
connected to make various circuits. Figure 1-1
(reproduced with permission of Wikipedia)
illustrates a typical prototype breadboard. A
complete description of the evolution to the modern
prototype breadboard may be found on Wikipedia
(http://en.wikipedia.org/wiki/Breadboard). The
outside rows of sockets are connected and provide
channels for supply voltages and grounding.
Sockets A, B, C, D, and E of each row are connected
Figure 1-1: Prototype Breadboard
as are sockets F, G, H, I, and J. Each socket will
generally accept one component lead. Alternatively,
each socket will accept one solid 22-guage wire.
This allows components that are inserted in a socket to be connected to other components
using jumper wires without the need for soldering. The spacing between columns E and F is
the same as manufacturers have established for DIP (Dual Inline Packed) ICs (Integrated
Circuits). The spacing between rows matches the spacing between adjacent IC pins. This
allows for easy prototyping of circuits using the DIP-ICs.
The oscilloscope is basically a visual waveform voltmeter. It displays DC voltages,
AC voltages, and combinations of AC and DC voltages as a function of time. The trace is
displayed on a calibrated screen which allows the user to measure the height of the signal.
By measuring the width between recurring points in the signal, the period can also be
measured. Once the period is known, it is an easy calculation to determine the frequency of
the signal. (See Pre-Lab Calculation 1.)
Most electronic circuits need a regulated DC voltage to operate properly. The
laboratory power supply can provide regulated DC and AC voltages. The power supply is
designed to maintain a set voltage within fixed limits for normal operation. Some ICs, will
only operate properly when the supply voltage is within a very narrow range. For a detailed
discussion of power supplies, the reader is directed to the Wikipedia article at
http://en.wikipedia.org/wiki/Power_supply. The laboratory power supply falls into the class
that is referred to as a linear power supply.
The Digital Multi-Meter (DMM) is generally the instrument of choice for measuring
DC and AC voltages and currents. It also provides the ability to directly measure resistances.
Many DMMs also have a continuity function that will produce an audible signal when it
senses a finite resistance (continuity) between two points. This allows the user to quickly
trace through a circuit looking for opens without the need to look at the meter. The internal
impedance of the DMM is generally quite high, on the order of 1 MΩ.
The Volt-Ohm-Miliameter (VOM) has a relatively high input impedance. However,
it is much lower than that of the DMM, on the order of 20 kΩ/V. This lower impedance is
one of reasons that the VOM has largely been replaced by the DMM. However, when stray
interference is an issue, the VOM may provide more accurate reading than the DMM. Also,
the VOM often has a better high frequency response.
Pre-Lab Reading:
Skim through Zekavat, ELECTRICAL ENGINEERING, Chapter 9
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 9.24
Problem 9.30
Problem 9.40
Required Materials:
1 – Laboratory power supply
1 – DVM
1 – VOM
1 – Audio Function Generator
1 – Oscilloscope
1 – Prototype Bread Board
1 – 10 kΩ resistor, ¼ W
1 – 100 kΩ resistor, ¼ W
1 – 330 kΩ resistor, ¼ W
1 – Resistor substitution box
Test leads and hook-up wire
Pre-Lab Calculations:
1. Common power in the U.S. is 60 Hz AC. Calculate the period of one cycle.
2. Calculate the value of the R1 in Figure 1-2 below, if the voltage across R2 is 909 mV.
Figure 1-2
3. Calculate the voltage across R1 and the voltage across R2 in Figure 1-3 below.
Figure 1-3
Procedure:
1. Turn on the DVM, the VOM, the Audio Function Generator, and the Oscilloscope.
Allow them to warm up for a few minutes. DO NOT TURN ON THE
LABORATORY POWER SUPPLY AT THIS TIME!!
2. Adjust the oscilloscope’s controls to get a clear trace on the screen. The trace should
not be too bright or damage to the screen may result.
3. Measure DC voltage using a 10 kΩ resistor, an oscilloscope, and a DVM.
a. Insert the leads of a 10 kΩ resistor in two unconnected sockets of the
prototype board.
b. Connect the resistor to the terminals of the low voltage DC power supply
using test leads.
c. Adjust the low voltage DC power supply to about the 20% point. NOW turn
on the laboratory power supply.
d. Copy Table 1-1 into your lab notebook.
e. Measure the voltage across the resistor using the oscilloscope and record the
value in your lab notebook.
f. Measure the voltage across the resistor using the DVM and record the value in
your lab notebook.
g. Turn off the laboratory power supply. Disconnect the test leads from the low
voltage DC power supply.
4. Measure AC voltage using a 10 kΩ resistor, an oscilloscope, and a DVM.
a. Connect the resistor to the terminals of the 6.3 V AC power supply using test
leads.
b. Turn on the laboratory power supply.
c. Copy Table 1-2 into your lab notebook.
d. Measure the voltage across the resistor using the oscilloscope and record the
value in your lab notebook.
e. Measure the voltage across the resistor using the DVM and record the value in
your lab notebook.
f. Turn off the laboratory power supply. Disconnect the test leads from the
6.3 V AC power supply.
g. Remove the 10 kΩ resistor from the breadboard.
5. Observe the output of a function generator.
a. Connect the output cable of the function generator to the oscilloscope. Make
sure the ground leads are connected together.
b. Observe and note the different waves that the function generator is capable of
generating. Vary the frequency of the waves.
c. Set the function generator for the square wave.
d. Copy Table 1-3 into your lab notebook.
e. Measure the period of the square wave at 50 Hz, 200 Hz, and 1 kHz, using the
oscilloscope.
f. Calculate the frequencies of the waves, using the measured periods.
6. Observe the effect of source impedance on delivered voltage
a. Keep the function generator connection to the oscilloscope from step 5 above.
b. Using the oscilloscope, set the function generator for a sinusoidal output of
exactly 2 VP-P at 1000 Hz.
c. Set the resistor substitution box for 100 Ω.
d. Connect the ground lead of the oscilloscope and function generator to one
terminal of the resistor substitution box and the other lead to the other
terminal. Make certain not to change the frequency or amplitude settings of
the function generator.
e. Copy Table 1-4 into your lab notebook
f. Observe and record the voltage across the resistor substitution box.
g. Disconnect the resistor substitution box from the function generator and the
oscilloscope.
h. Measure the actual resistance of the resistor substitution box using the DVM.
Record the actual resistance in Table 1-4.
i. Using the data captured in Table 1-4, calculate the output impedance of the
function generator. Refer to Pre-Lab Calculation 2 above.
7. Observe the effect of input impedance on voltage measurements.
a. Set the low voltage DC power supply to 10 V using the DVM.
b. Copy Table 1-5 into your lab notebook.
c. Measure the actual resistance of the 330 kΩ resistor and the 100 kΩ resistor
and record the values in Table 1-5
d. Make sure the power supply is off, but do not disturb the settings. Wire the
circuit shown in Figure 1-4 below on the prototype bread board.
Figure 1-4
e. Copy Table 1-6 into your lab notebook.
f. Turn on the low voltage DC power supply.
g. Measure the voltage across R1 and R2 using the DVM and record the results
in Table 1-6.
h. Measure the voltage across R1 and R2 using the VOM and record the results
in Table 1-6.
i. Calculate the theoretical voltage across R1 and R2 using the actual resistance
values from Table 1-5. Record the results in Table 1-6. Refer to Pre-Lab
Calculation 3 above.
8. Clean up your lab station.
a. Turn off the laboratory power supply, the DVM, the VOM, the Audio
Function Generator, and the Oscilloscope.
b. Remove any components from the prototype breadboard.
c. Return the components and test leads to their proper position.
d. Clean up any scrap paper and waste and generally straighten up around your
work station.
Results:
Measured Voltage
Oscilloscope
DVM
Table 1-1: DC Voltage Across a 10 kΩ Resistor
Measured Voltage
Oscilloscope
DVM
Table 1-2: AC Voltage Across a 10 kΩ Resistor
Function
Generator
Frequency
Period
Calculated
Frequency
50 Hz
200 Hz
1 kHz
Table 1-3: Measured Period and Calculated Frequency from Function Generator
Measured Value
Loaded Circuit
using
Oscilloscope
Actual Resistance
of Substitution
Box
Output
Impedance of
Function
Generator
Table 1-4: Measurements to Determine Internal Impedance
Nominal Resistance Measured Resistance
R1
R2
Table 1-5: Resistance Values
Voltage
Measured Value R1
Using a DVM
R2
Measured Value R1
Using a VOM
R2
Calculated
Value Based
upon Measured
Resistance
R1
R2
Table 1-6: Voltage Across Each Resistor
Lab Notebook:
1. Reflect on using a prototype breadboard to wire a circuit. What are the advantages?
What are the limitations?
2. Reflect on the use an oscilloscope to measure DC and AC voltages.
3. Reflect on the use a DVM to measure DC and AC voltages.
4. Reflect on the output of a function generator. What is the effect of source impedance
on delivered voltage?
5. What is the effect of input impedance on voltage measurements?
Lab 2: Transformers and Impedance Matching
Learning Objectives:
1. Determine the no-load and full-load operating conditions for a single phase
transformer.
2. Observe the power delivered to a load with and without impedance matching.
Introduction
The first thing to notice about a transformer is that it is only able to operate with an
AC signal. Transformers will NOT work with DC signals. The primary coil of the
transformer converts the time-varying (AC) voltage to a time-varying magnetic field. This
time-varying magnetic field then produces a time-varying (AC) electric voltage at the
secondary side of the transformer.
The ratio of the output voltage to the input voltage is called the turns ratio: the turns
ratio is also the ratio of the number of turns of the primary coil to the number of turns of the
secondary coil. Although this lab tells you the number of primary and secondary turns for
the transformer under consideration, generally, the only information available is the
maximum input and output voltages.
Transformers are commonly used for a variety of applications. One very common
application, which we will be exploring in this lab, is impedance matching. The maximum
power is transferred from a source to a load when the load impedance is the equivalent to the
source impedance. If the two impedances are not the same, then a proper transformer can be
interposed between the source impedance and the load impedance to convert the load
impedance to the equivalent of the source impedance – thus creating a situation where the
maximum power will be transferred to the load.
The load impedance that the source “sees” through the transformer is
𝑍′ =
1
𝑍 .
𝑁2 𝐿
With the proper choice of a transformer, the impedance of a load can be “matched” to
the internal impedance of the source.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Chapter 3
Pre-Lab Exercises:
Problem 1
A 115/28V transformer has 56 turns on its low voltage side. How many turns does it
have on its high voltage side? What is its turns ratio when it is used as a step-down
transformer? As a step-up transformer?
Problem 2
A transformer is used to match an 8Ω speaker to a 500Ω audio line. What is the turns
ratio of the transformer? What is the input voltage and the output voltage when 15W is being
delivered to the speaker?
Required Materials:
1 – Laboratory power supply
2 – Digital multimeters
1 – Simpson model 370 ammeter
1 – AC voltmeter
1 – Simpson wattmeter, 0-4 A, 0-150 V
1 – Single-phase transformer, 80:40 V, 60 Hz, 80 VA (NP = 280 turns, NS = 140 turns)
3 – Slide-wire rheostats, 0-100 Ω, 0-5 A
2 – Three-pole insertion switches
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the turns ratio for the transformer specified above using the primary and
secondary voltage.
2. Calculate the turns ratio for the transformer specified above using the number of
primary turns and the number of secondary turns.
3. Calculate the current and the power dissipated across the load resistor, RL, in the
circuit shown in Figure 2- 1 for each of the resistance values in Table 2- 1
Figure 2- 1
RL (Ohms)
25
40
55
70
85
100
115
130
145
160
I (Amps)
P (Watts)
Table 2- 1
4. Calculate the resistive power dissipated across the load resistor, RL, in the circuit
shown in Figure 2- 3 for a load resistance of 25 Ω using a 80:40 V, 60 Hz, 80 VA
transformer.
Procedure:
1. Measure and record the primary winding resistance and the secondary winding
resistance of the transformer.
2. Connect the circuit shown in Figure 2- 2.
Figure 2- 2
a.
b.
c.
d.
Set the variable AC supply to 0V before connecting to the circuit.
Have your lab instructor inspect your circuit and initial your lab notebook.
Switch on the power and slowly increase the supply voltage to 80 V.
Measure and record the primary voltage, the primary current, and the primary
power.
e. Measure and record the secondary voltage.
f. Calculate and record the voltage transformation ratio.
g. Switch off the power.
3. Connect the circuit shown in Figure 2- 3
Figure 2- 3
a. Calculate the resistance that will draw the rated secondary current at the rated
secondary voltage.
b. Adjust the slide resistor to the calculated value and connect into the circuit.
c. Reset the AC voltage to 0 V.
d. Have your lab instructor inspect your circuit and initial your lab notebook.
e. Switch on the power and slowly increase the supply voltage until the rated
voltage and current are observed at the load
f. Measure and record all voltages and currents and the supply power.
g. Calculate and record the current transformation ratio.
h. Calculate and record the transformer’s operating efficiency and voltage
regulation. (Hint: review labs 6 and 7.)
i. Switch off the power.
j. Set the load resistor, RL, to 25 Ω. Reset the AC voltage to 0 V.
k. Switch on the power and slowly increase the supply voltage until the rated
voltage and current are observed at the load
l. Measure and record all voltages and currents and the supply power.
m. Switch off the power.
4. Connect the circuit shown in Figure 2- 4.
Figure 2- 4
a.
b.
c.
d.
e.
Set the variable AC supply to 0V before connecting to the circuit.
Use two slide resistors in series for the load resistance.
Have your lab instructor inspect your circuit and initial your lab notebook.
Switch on the power and slowly increase the supply voltage to 80 V.
Adjust the load resistance to match (each of) the load currents, IL, calculated
in Table 2- 1 above. Measure the load voltage, VL. Compute the power
dissipated, PL, and the load resistance, RL, for each value of IL.
5. Clean up your lab station and put all material away.
Results:
1. Using the turns ratio and the calculated value of the load resistance from procedure
step 3.a, calculate the value of the load resistance reflected to the source.
2. Using the data gathered in procedure step 1 and 3, calculate the winding heating
losses. Calculate the total losses. What is the percentage of the winding heating
losses to the total losses.
3. Calculate the percent of the no-load primary current to the rated current.
4. Create a table to display the data gathered in procedure step 4.
5. Make graphs of P vs. RL for the data produced in the pre-lab calculation in Table 2- 1
and in procedure step 4.
6. Calculate the theoretical maximum power that can be transferred to the load in Figure
2- 3. (NB: Don’t ignore the winding resistances measured in procedure step 1.)
Lab Notebook:
1. Compare and comment on the voltage transformation ratio calculated in step 2 to the
current transformation ratio calculated in procedure step 3.
2. Compare and comment on the reflected value of the load resistance calculated in the
results item 1 with the ratio of the primary voltage to the primary current measured in
procedure step 3.f.
3. What is the percentage of the no-load primary current measured in procedure step 2 to
the rated current.
4. Compare and comment on the actual power produced, the predicted power produced,
and the maximum power in procedure step 4.
5. Compare and comment on the actual power produced, the predicted power produced,
and the maximum power in procedure step 3.l.
Lab 3: Balanced Three-Phase Circuits
Learning Objectives:
1. Observe the relationships between line and phase voltages and currents for balanced
three-phase loads.
2. Calculate and measure the power delivered to balanced three-phase loads.
Caution: 208 VAC is used for this experiment. You must have your instructor check
your wiring before applying power at each of the steps listed. Failure to do so could
result in injury and WILL result in failure of this lab.
Introduction
Three balanced voltages that are displaced 120° in phase from each other has the
property of delivering constant instantaneous power. Three-phase motors also have a nonzero starting torque. These, and other advantages has resulted in most AC power being
generated and distributed as three-phase. Furthermore, most industrial motors are threephase.
The three phases can be connected in a wye (or Y, sometime called a T or star)
configuration or a delta (or Δ, sometimes called a pi or ∏) configuration. As explained in
your text, there is a fixed relation between the value of the phase voltage and current (that
generated from each phase of the generator) and the line voltage and current (that measured
between the lines), depending upon the configuration of the load.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Chapter 5
Pre-Lab Exercises:
Zekavat, ELECTRICAL E NGINEERING,
Problem 5.10
Problem 5.22 (part 1 only)
Required Materials:
1 – Laboratory power supply with three-phase, 208/120 VAC, 60 Hz capability
1 – Multi-range AC ammeter
1 – Simpson 260 VOM
1 – 0 - .75, 1.5 kW wattmeter
3 – 100 Ω, 3 A, slide-wire rheostat
3 – decade capacitor boxes
1 – set of insertion switches
Test leads and hook-up wire
Pre-Lab Calculations:
1. The line-to-neutral voltages in Figure 3- 1 are each 120 VAC. Calculate the line-toline voltages, the line currents, and the neutral current for this circuit.
2. Calculate the power in each leg of the circuit in Figure 3- 1.
3. The line-to-neutral voltages in Figure 3- 3 are each 120 VAC. Calculate the line-toline volages, the line currents, and the load currents for this circuit.
4. Calculate the power in each leg of the circuit in Figure 3- 3.
Procedure:
1. Locate the 208 VAC, 60 Hz AC terminals on the laboratory power supply. The
voltage appears between the terminals when the switch on power supply is thrown.
The magnitude of the voltage can not be adjusted. Each of these three lines should
have a 15 A fuse in series with it. Locate the metal ground terminals on the power
supply. The voltage between any one of the three-phase lines and ground will be 120
VAC.
2. Connect the balanced wye load shown in Figure 3- 1 to the 208 VAC three-phase
power supply. Put an insertion switch box at each point in the circuit where the
current is to be measured. (Suggestion: Use Red wire for the a phase, Black wire for
the b phase, Blue wire for the c phase, and White wire for the neutral connection.)
Figure 3- 1
3. Have your instructor check your wiring and initial your lab notebook.
4. Apply power to the circuit and measure:
a. line-to-neutral voltages: 𝑉𝑎𝑛 , 𝑉𝑏𝑛 , 𝑉𝑐𝑛
b. line-to-line voltages: 𝑉𝑎𝑏 , 𝑉𝑏𝑐 , 𝑉𝑐𝑎
c. line currents: 𝐼𝑎 , 𝐼𝑏 , 𝐼𝑐
d. neutral line current: 𝐼𝑛
5. Check the data obtained by comparing to the calculated values.
6. Turn off the power. Have your instructor check your calculation and initial your lab
notebook,
7. Measure the power delivered to the balanced wye using the “three wattmeter
method.” Connect the voltage sensing lead shown in Figure 3- 2 to the neutral
terminal. Connect the insertion switch probe to one of the insertion switches (line a,
b, or c). Consult your calculated values to determine the appropriate current range
and voltage range for the wattmeter.
Figure 3- 2
8. Have your instructor check your wiring and initial your lab notebook.
NB. Whenever you are using a wattmeter, be alert for downscale readings. A low
power factor may create a situation that appears to be low power, yet the voltage and
current are so far out of phase that the circuit could destroy the wattmeter.
9. Turn on the power and measure the power for this leg.
10. Turn off the power, move the insertion switch probe to the next leg, turn on the power
and measure the power for this leg.
11. Repeat step 10 for the final leg. Turn off the power.
12. Check the data obtained by comparing to the calculated values.
13. Connect the balanced delta load shown in Figure 3- 3 to the208 VAC three-phase
power supply. Use an insertion switch at each location where a current is to be
measured.
Figure 3- 3
14. Have your instructor check your wiring and initial your lab notebook.
15. Apply power to the circuit and measure:
a. line-to-line voltages: 𝑉𝑎𝑏 , 𝑉𝑏𝑐 , 𝑉𝑐𝑎
b. line currents: 𝐼𝑎 , 𝐼𝑏 , 𝐼𝑐
c. load currents: 𝐼𝑎𝑏 , 𝐼𝑏𝑐 , 𝐼𝑐𝑎
16. Check the data obtained by comparing to the calculated values.
17. Turn off the power. Have your instructor check your calculation and initial your lab
notebook.
18. Measure the power delivered to the balanced delta using the “two wattmeter method.”
Connect the voltage sensing lead shown in Figure 3- 2 to one of the three-phase lines.
Connect the insertion switch probe an insertion switch on one of the other two lines.
Consult your calculated values to determine the appropriate current range and voltage
range for the wattmeter.
19. Have your instructor check your wiring and initial your lab notebook.
NB. Whenever you are using a wattmeter, be alert for downscale readings. A low
power factor may create a situation that appears to be low power, yet the voltage and
current are so far out of phase that the circuit could destroy the wattmeter.
20. Turn on the power and measure the power for this leg.
21. Turn off the power, move the insertion switch probe to the next leg, turn on the power
and measure the power for this leg. Turn off the power.
22. Check the data obtained by comparing to the calculated values.
23. Clean up your work station and put all equipment and components away.
Results:
For each of the circuits studied, make a table to compare measured and calculated values.
Lab Notebook:
1. Each time you used the wattmeter, you were cautioned to be alert for downscale
readings. Comment on this caution.
2. Power on the wye circuit was measured using the “three wattmeter method” whereas
power on the delta circuit was measure using the “two wattmeter method.” Could the
two wattmeter method be used with the wye? If so, under what circumstances could
it be used. Why could it be used on the delta? Could the three wattmeter method be
used with the balanced delta?
Lab 4: Ideal Amplifier Circuits
Learning Objectives:
1. Observe the parameters for the equivalent circuit for an ideal amplifier.
2. Understand the properties of gain, input impedance, and output impedance.
Introduction
The amplifier is, perhaps, the most important functional block found in an electronic
system. Amplifiers are used to increase (amplify) the electrical signal from such sensors as
strain gauges (commonly used by mechanical engineers), flow meters (commonly used by
chemical engineers), and position sensors (commonly used by civil engineers and industrial
engineers).
The output of an ideal amplifier produces a voltage that is proportional to the input
voltage:
𝑣𝐿 (𝑡) = 𝐴𝑣𝑆 (𝑡)
where 𝐴 represents the voltage gain of the amplifier, 𝑣𝑆 represents the input (or source)
voltage, and 𝑣𝐿 represents the output (or load) voltage. If 𝐴 is a positive number then the
amplifier is a noninverting amplifier and the phase of the output voltage directly tracks the
phase of the input voltage. If 𝐴 is negative, then the amplifier is an inverting amplifier. The
output voltage of an ideal inverting amplifier is always exactly 180° out of phase with the
input voltage.
The input voltage seen by the ideal amplifier is a function of the input resistance
(impedance) of the amplifier as well as the output resistance (impedance) of the source.
Similarly, the output voltage, 𝑣𝐿 , is a function of the output resistance (impedance) and the
load resistance (impedance).
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Section 7.5
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 7.69
Required Materials:
1 – Dual ±15 VDC power supply
1 – DVM
1 – Operational amplifier, integrated, general purpose
1 – Audio Function Generator
1 – Oscilloscope
1 – Prototype Bread Board
1 – 100 Ω resistor, ¼ W
1 – 1 kΩ resistor, ¼ W
1 – 470 Ω resistor ¼ W
1 – 1.5 kΩ resistor, ¼ W
1 – 0.1 µF capacitor, 25 VDC
Test leads and hook-up wire
Pre-Lab Calculations:
1. Using Figure 4-1 and Figure 4- 2, calculate 𝑍𝑖 in terms of 𝑉𝑜𝑐 , 𝑉𝑖𝑛 , and 𝑉𝑜 .
2. Using Figure 4-1 and Figure 4- 2, calculate 𝐴 in terms of 𝑉𝑖𝑛 and 𝑉𝑜 .
3. Using Figure 4- 2 and Figure 4- 3, calculate 𝑍𝑜 in terms of 𝑉𝑜 , 𝑉𝐿 , and 𝑅𝐿
Figure 4- 1
Figure 4- 2
Figure 4- 3
Procedure:
1. Determine the output impedance of your function generator for a 500 Hz sinusoidal
waveform. (Hint: review Lab 1, step 6)
Figure 4- 4
2. Breadboard the circuit shown in Figure 4- 4. This is the amplifier we will test to
determine its equivalent circuit.
a. Carefully insert the leads of the operational amplifier in the holes of the circuit
board so that the amplifier bridges the center groove. It is important that the
leads of the op-amp do not bend when this is done.
b. Get the lead numbers for the op-amp from your lab instructor. Sketch this
circuit in your lab manual with the correct lead numbers annotated. Connect
the components to the op-amp. (NB: Pin 1 has a notch or a dot near it.)
c. Check the output of the dual ± 15 V power supply before making the
connections to the op-amp.
d. Have your instructor check your wiring and intial next to the schematic in
your lab manual.
3. Turn on the 15 V power supply. Measure the input impedance and the open-circuit
voltage gain of the amplifier which you breadboarded.
a. Set the function generator of an open-circuit voltage of 0.2 Vp-p (See Figure 4) at a frequency of 500 Hz.
Figure 4- 5
b. Connect the function generator to the amplifier (Figure 4- ) and measure Vin
and Vo.
Figure 4- 6
c. Calculate Zi and A. (Hint: refer to your pre-lab calculations.)
4. Measure the output impedance of the amplifier.
a. Recall the open-circuit voltage Vo measured in step 3.b above.
b. Add a 1.5 kΩ load resistor as shown in Figure 4- .
Figure 4- 7
c. Measure the voltage across the load. (NB: Do not change the frequency of the
function generator.)
d. Calculate the output impedance, Zo. (Hint: Refer to the pre-lab calculations.)
5. Measure the open-circuit voltage gain for the amplifier (amplitude and phase shift) at
the following frequencies: 200 Hz, 500 Hz, 1 kHz, 5 kHz, and 10 kHz, using the
circuit of Figure 46. Clean up your lab station and put all the material away.
Results:
1. Create a table to show the
a. Function generator output impedance
b. Amplifier input impedance
c. Amplifier open-circuit voltage gain
d. Amplifier output impedance
at 500 Hz.
2. Create a table to show the amplifier open-circuit voltage gain (amplitude and phase
shift) at 200 Hz, 500 Hz, 1 kHz, 5 kHz, and 10 kHz. The table should show the
amplitude both as raw gain and in dB. Show the formulae that went into the
calculations for this table.
3. Make Bode plots for the amplifier’s open-circuit voltage gain.
a. Use semi-log graph paper or MatLab’s plotting capability.
b. Plot 20 log (Vo/Vin) vs frequency on one graph.
c. Plot the phase angle between Vo and Vin vs frequency on another graph.
Lab Notebook:
1. Include the tables and graphs produced in the Results section above.
2. Using the Bode plots, determine the corner frequency for the amplifier’s frequency
response.
3. Recall from the introduction, that an ideal amplifier should introduce no phase shift
(or exactly 180° phase shift). Comment upon how the frequencies for which this
particular op-amp configuration approximates an ideal amplifier.
Lab 5: Frequency Response of a Passive Network
Learning Objectives:
1. Understand the frequency response of a low-pass filter.
2. Observe the logarithmic relation of the magnitude and phase of the output relative to
frequency.
Introduction
The frequency response of a system is the measure of ratio of the system output to the
system input as a function of frequency. In this course we are looking at electrical systems;
however, the same concepts hold for mechanical systems, for chemical systems, for
ecological systems, and even for financial systems. With electrical systems, we naturally
consider circuit input and output.
The inputs and outputs to a circuit may be currents or voltages. The most commonly
used transfer function relates output voltage to input voltage, as shown in equation 6.1 of
your text. The four possible transfer functions are shown in equation 6.8 of your text. The
reader interested in the other three transfer functions is directed to look at the chapter on twoport networks which will generally be toward the end of the text used for their first circuits
course.
The low pass filter passes low frequency signals with little or no attenuation (as the
name implies). The corner frequency (sometimes called the cutoff frequency, or the 3 dB
frequency) represents the point at which the output voltage is 1/√2 = 0.707 times the input
voltage. At frequencies above the corner frequency, the output signal is attenuated to less
than 0.707 times the input voltage.
The decibel (dB) is 1/10 of a bel, where the bel is defined as the base 10 logarithm of
the ratio of the output power to the input power. The decibel is a more convenient unit of
measure than the bel, which is rarely used. The formula is:
𝑑𝐵 = 10 log10
Recall that Watt’s Law tells us that 𝑃 =
𝑑𝐵 = 10 log10
2
𝑉𝑜𝑢𝑡
2
𝑉𝑖𝑛
= 20 log10
𝑉𝑜𝑢𝑡
𝑉𝑖𝑛
.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Chapter 6
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 6.1
Problem 6.2
𝑉2
𝑅
𝑃𝑜𝑢𝑡
𝑃𝑖𝑛
. Substituting yields:
Required Materials:
1 – DVM
1 – Audio Function Generator
1 – Oscilloscope
1 – Prototype Bread Board
1 – 0.1 µF capacitor, 25 VDC
1 – 2.2 kΩ resistor, ¼ W
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the dB attenuation when the output power of a circuit is ½ the input power.
Show your work.
𝑉 (𝑓)
2. Using complex numbers and phasors, compute the transfer function, 𝐻(𝑓) = 𝑉𝑜𝑢𝑡(𝑓)
for the circuit in Figure 5- 1 if R = 2.2 KΩ and C = 0.1 µF.
3. Calculate the corner frequency, 𝑓𝑐 , for the circuit described in 2 above.
𝑖𝑛
Figure 5- 1
Procedure:
1. Wire the filter of Figure 5- 1 on the prototype board.
2. Connect the function generator to the terminals at the left and the oscilloscope to the
terminals on the right.
3. Vary the frequency of the function generator from 0.1𝑓𝑐 to 10𝑓𝑐 (refer to prelab
calculation 3, above). Look at a minimum of 10 to 20 frequencies, including the
corner frequency itself.
4. At each frequency, measure the magnitude and phase angle of the output.
5. Clean up your work station and put all equipment and components away.
Results:
1. Calculate the dB for each magnitude.
2. On standard graph paper (you may plot directly into your lab book if it is quadrille),
plot the output magnitude versus frequency.
3. On standard graph paper, plot the output phase angle (in degrees) versus frequency.
4. On semi-log graph paper, plot the output magnitude (in dB) versus frequency. Insert
this plot into your lab notebook. At a minimum, all four corners must be attached.
Better is to tape across all four sides.
5. On semi-log graph paper, plot the output phase angle (in degrees) versus frequency.
Insert this plot into your lab notebook.
6. Draw asymptotic lines on the Bode plots (the semi-log plots drawn in steps 4 and 5
above).
7. Determine the corner frequency using the Bode plots.
Lab Notebook:
1. Compare the calculated frequency response to the measured frequency response.
Comment on any discrepancies.
2. Compare and comment on the calculated corner frequency to the measured corner
frequency.
3. What is the actual magnitude and phase angle at the calculated corner frequency and
at the measured corner frequency?
Lab 6: Operational Amplifier Circuits
Learning Objectives:
1. Observe the characteristics of several common closed-loop operational amplifier
circuit configurations. Specifically:
a. the inverting amplifier;
b. the summing amplifier;
c. the non-inverting amplifier;
d. the voltage follower; and
e. the integrating amplifier.
Introduction
The operational amplifier (commonly called an op-amp) is a collection of several
dozen transistors, resistors, diodes, and capacitors configured into a circuit which provides an
amplification function which can provide a summing or integration operation (hence the
name, operational amplifier). These components are generally manufactured on a single
piece of silicon crystal (called a chip). Circuits manufactured in this manner are called
integrated circuits (ICs). The manufacture of such circuits does not cost significantly more
than the manufacture of single transistors, resistors, or capacitors.
In this lab, we will see that inexpensive IC op-amps can be combined with individual
resistors and capacitors to easily achieve amplification (inverting and non-inverting),
summation, and integration. We will also look at the voltage follower. The voltage follower
circuit allows for the isolation of a low current source from the load. The voltage follower is
an important enough configuration that ICs are available that package several voltage
follower circuits in a single IC.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Section 7.5
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 7.71
Required Materials:
1 – Dual ±15 VDC power supply
1 – DVM
1 – Operational amplifier, integrated, general purpose
1 – Audio Function Generator
1 – Oscilloscope
1 – Prototype Bread Board
1 – 1 kΩ resistor, ¼ W
1 – 2.2 kΩ resistor, ¼ W
2 – 10 kΩ resistor, ¼ W
1 – Resistor substitution box
1 – 0.1 µF capacitor, 25 VDC
Test leads and hook-up wire
Pre-Lab Calculations:
1. Using Figure 6-1 calculate 𝑉𝑜 in terms of 𝑉𝑖𝑛 and 𝑅𝐹 .
2. Calculate 𝑉𝑜 for the circuit in Figure 6-2.
3. Using Figure 6-3, calculate 𝑉𝑜 in terms of 𝑉𝑖𝑛
4. Calculate 𝑉𝑜 for the circuit in Figure 6- 4 in terms of 𝑉𝑖𝑛 .
Procedure:
1. Carefully insert the leads of the operational amplifier in the holes of the circuit board
so that the amplifier bridges the center groove. It is important that the leads of the opamp do not bend when this is done.
a. Get the lead numbers for the op-amp from your lab instructor. Sketch each
circuit in your lab manual with the correct lead numbers annotated.
b. Check the voltage outputs of the dual ±15 V power supply. If they are
correct, turn the power supply off and connect it to the power pins for the opamp. (Note that the power leads are not shown in schematics, Figure 6-1 thru
6-5. This is common schematic practice for op-amps. Make sure to connect
the +15 V to the correct pin and the -15 V to the correct pin.) Do NOT turn
on the dual power supply at this time.
2. Connect the circuit shown in Figure 6-1. Use the resistor substitution box for 𝑅𝐹 .
(NB: Pin 1 has a notch or a dot near it.)
Figure 6- 1
a. Have your instructor check your wiring and initial next to the schematic in
your lab manual.
b. Set the function generator for a 0.2 V peak-to-peak sine wave at 1 kHz.
Connect the function generator to 𝑉𝑖𝑛 .
c. Turn on the dual ±15 V power supply.
d. Measure 𝑉𝑜 for values of 𝑅𝐹 from 1 kΩ to 47 kΩ.
e. Set 𝑅𝐹 to 10 kΩ. Measure 𝑉𝑜 as you vary the frequency of the sine wave from
20 Hz to 100 kHz.
f. Set the frequency to 1 kHz. Gradually increase the amplitude of 𝑉𝑖𝑛 to the
point of distortion in 𝑉𝑜 . Record 𝑉𝑖𝑛 and 𝑉𝑜 at this point.
g. Turn off the dual ±15 V power supply.
3. Connect the circuit shown in Figure 6-2. Turn on the power supplies. Use the DVM
to measure the actual input voltages and 𝑉𝑜 . Turn off the power supplies.
Figure 6- 2
4. Connect the circuit shown in Figure 6-3.
Figure 6- 3
a. Set the function generator for a 0.2 V peak-to-peak sine wave at 1 kHz.
Connect the function generator to 𝑉𝑖𝑛 .
b. Turn on the dual ±15 V power supply.
c. Measure 𝑉𝑜 .
d. Turn off the dual power supply.
5. Connect the circuit shown in Figure 6- 4.
Figure 6- 4
a. Set the function generator for a 0.2 V peak-to-peak SQUARE wave at 1 kHz.
Connect the function generator to 𝑉𝑖𝑛 .
b. Turn on the dual ±15 V power supply.
c. Observe 𝑉𝑜 .on the scope and sketch the waveform.
d. Set the frequency to 500 Hz.
e. Observe 𝑉𝑜 .on the scope and sketch the waveform.
f. Turn off the dual power supply.
6. Connect the circuit shown in Figure 6- 5
Figure 6- 5
a. Set the function generator for a 0.2 V peak-to-peak sine wave at 1 kHz.
b. Connect a 1 kΩ resistor between the terminals of the function generator.
c. Measure the voltage across the resistor.
d. Connect the function generator to 𝑉𝑖𝑛 .
e. Turn on the dual power supply.
f. Measure 𝑉𝑜 .
g. Turn off the dual power supply.
h. Connect the 1 kΩ resistor between 𝑉𝑜 and ground.
i. Turn on the dual power supply.
j. Measure the voltage across the resistor.
7. Turn off all power supplies and equipment. Disassemble the circuit board and put
everything away.
Results:
1. Create a table to show the actual and theoretical output voltage for the various values
of 𝑅𝐹 used for the circuit in Figure 6-1.
2. Create a table to show the actual and theoretical output for each of the various
frequencies used in step 2.e above.
Lab Notebook:
1. What is the operation that each circuit performs?
2. What is the bandwidth of the amplifier in step 2.e above?
3. Why does the output voltage become distorted in step 2.f above? What is the
significance of the voltage, 𝑉𝑜 , where this occurs?
4. Comment on the voltage drops measured across the resistor in step 6 above.
Lab 7: Rectifiers and Capacitor Filters
Learning Objectives:
1. Learn to test diodes.
2. Observe the characteristics of a half-wave rectifier.
3. Observe effect of a capacitor filter on a rectified circuit.
Introduction
An ideal diode is the electrical equivalent of a one-way (or check) valve in a
hydraulic system. When the ideal diode is forward biased, it operates as a short circuit (or
closed switch). When the ideal diode is reverse biased, it operates as an open circuit (or
opened switch).
When an unbiased AC signal is connected to a diode, the diode will conduct during
the positive portion of the cycle and will function as an open circuit during the negative
portion of the cycle. This process is called rectification. The rectified output is shown here
in Figure 7-1.
Figure 7- 1
We see that the output of the half-wave rectifier only provides a voltage during one
𝑉
half of the cycle. Since the period, 𝑇, is 2π radians in length, the average voltage 𝑉𝑑𝑐 = 𝜋𝑚 .
𝑉
The average current is then 𝐼𝑑𝑐 = 𝑅𝑑𝑐 and the peak inverse voltage, PIV, is approximately
equally to the peak forward voltage, 𝑉𝑚 . This could be sufficient for applications such as a
battery charger. However, for most electronic applications, a more steady voltage is required
for the entire cycle.
An RC filter can help smooth the bumps from this output. Recall that the time
constant (𝜏 = 𝑅𝐶) of an RC circuit determines the rate at which the capacitor discharges.
Therefore, with the proper choice of resistance and capacitance, an RC filter can be designed
to provide a voltage during the portion of the AC cycle when the diode is not conducting.
The voltage output waveform at the output of a rectifier with a capacitor filter would look
somewhat like that shown in Figure 7- 2
Figure 7- 2
Assuming the ripple is approximately a triangular wave form:
𝑉𝑑𝑐 = 𝑉𝑚 −
𝑉𝑟(𝑝−𝑝)
and
2
𝑉𝑟(𝑟𝑚𝑠) =
𝑉𝑟(𝑝−𝑝)
2√3
.
For a half-wave rectifier:
𝑉𝑑𝑐 = [
−(1 + 𝛼) + √(1 + 𝛼)2 + 4𝛼
𝑉𝑚 ]
2𝛼
where
𝛼=
1
Recall that 𝑓 = 𝑇 and 𝐼𝑑𝑐 =
𝑉𝑑𝑐
𝑅
1
.
4𝑓𝑅𝐶
. The 𝑃𝐼𝑉 ≅ 2𝑉𝑚 .
There are several measures of effectiveness used for filters (these apply to any filter,
not just the RC filter). The ripple factor, which is ideally 0, is defined as
𝑟=
𝑉𝑟(𝑟𝑚𝑠)
.
𝑉𝑑𝑐
The percent of ripple, which is also ideally 0, is defined as
%𝑟 =
𝑉𝑟(𝑟𝑚𝑠)
∙ 100%.
𝑉𝑑𝑐
The percent voltage regulation, which is again ideally 0, is defined as
%V.R. =
𝑉𝑁𝐿 − 𝑉𝐹𝐿
𝑉𝐹𝐿
where 𝑉𝑁𝐿 and 𝑉𝐹𝐿 are the no-load and full-load dc output voltages, respectively.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Sections 7.1 – 7.3.
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 7.10
Problem 7.11
Problem 6.8
Required Materials:
1 – Laboratory power supply
1 – DVM
1 – Oscilloscope
1 – DC milliameter
1 – Prototype Bread Board
1 – Rectifier diode
1 – 1.5 kΩ resistor, ¼ W
1 – Resistor substitution box
1 – 10 µF electrolytic capacitor
1 – 100 µF electrolytic capacitor
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the period of a 60 Hz signal.
2. Calculate the time constant for an RC circuit with a 1.5 kΩ resistor and a 10 µF
capacitor.
3. Calculate the percentage of the 60 Hz signal represented by one time constant for the
filter in calculation 2 above.
4. Calculate the time constant for an RC circuit with a 1.5 kΩ resistor and a 100 µF
capacitor.
5. Calculate the percentage of the 60 Hz signal represented by one time constant for the
filter in calculation 4 above.
6. Calculate the percentage attenuation in one time-constant.
7. Assume the peak value of the signal in Figure 7- 3 is 19 V. Calculate the DC voltage,
𝑉𝑑𝑐 ; the DC current, 𝐼𝑑𝑐 ; and the peak inverse voltage, PIV, across the diode.
8. Assume the peak value of the signal in Figure 7- 4 is 19 V and the value of the
capacitor is 100 µF. Calculate the DC voltage, 𝑉𝑑𝑐 ; the DC current, 𝐼𝑑𝑐 ; and the peak
inverse voltage, PIV, across the diode. Also calculate the peak-to-peak ripple
voltage, 𝑉𝑟(𝑝−𝑝) , and the rms value of the ripple voltage, 𝑉𝑟(𝑟𝑚𝑠) .
9. Calculate the percent ripple and percent voltage regulation of the filtered rectifier in
calculation 8 above
Procedure:
1. Test your diode using the DVM. The diode must NOT be in a circuit for this test.
a. Connect the black test lead to the black COM jack and the red test lead to the
red V-Ω jack.
b. Push in the Ω (ohms) function button.
c. Simultaneously push the 200 and the 2k range buttons to the in position.
d. Connect the red test lead to the anode and the black test lead to the cathode of
the diode. Turn on the DVM. A DVM reading of 1 (over-range indicator)
MAY mean the diode is defective (open). A DVM reading of 00.0 DOES
mean the diode is defective (shorted).
e. Reverse the test leads (connect the red test lead to the cathode and the black
test lead to the anode). Unless the meter (eventually) indicates 1 (with the
over-range indicator on), the diode is defective.
f. If your diode is defective, return it to your lab instructor (make sure to tell the
instructor that the diode is defective), get another one, and repeat the test.
2. Construct the circuit shown in Figure 7- 3.
Figure 7- 3
a. Measure the actual value of the 1.5 kΩ resistor. Measure the actual voltage
output from the 12.6 V rms supply. Sketch the circuit shown in Figure 7- 3 in
your lab notebook with the correct values.
b. Insert the components on your breadboard.
c. Make certain the power is OFF and connect the 12.6 V rms supply.
d. Have your lab instructor check your wiring and initial your lab notebook.
e. Turn on the power supply.
f. Observe the input and output waveforms with your oscilloscope. Sketch them
into your lab notebook. Make certain to include voltage and time dimensions.
g. Measure and record the average load voltage, 𝑉𝑑𝑐 , using the DVM. (NB: make
certain it is set on DC.)
h. Measure and record the average load current, 𝐼𝑑𝑐 , using the DC milliameter.
i. Measure and record the PIV (peak inverse voltage) across the diode using the
oscilloscope.
j. Turn OFF the power supply.
3. Construct the circuit shown in Figure 7- 4 using the 10 µF electrolytic capacitor.
Figure 7- 4
a. Sketch the circuit shown in Figure 7- 4in your lab notebook with the correct
values.
b. Insert the components on your breadboard. Make certain to observe the
polarity marks on the capacitor.
c. Make certain the power is OFF and connect the 12.6 V rms supply.
d. Have your lab instructor check your wiring and initial your lab notebook.
e. Turn on the power supply.
f. Observe the input and output waveforms with your oscilloscope. Sketch them
into your lab notebook. Make certain to include voltage and time dimensions.
g. Turn OFF the power supply.
4. Construct the circuit shown in Figure 7- 4 using the 100 µF electrolytic capacitor.
a. Sketch the circuit shown in Figure 7- 4 in your lab notebook with the correct
values.
b. Insert the components on your breadboard. Make certain to observe the
polarity marks on the capacitor.
c. Make certain the power is OFF and connect the 12.6 V rms supply.
d. Have your lab instructor check your wiring and initial your lab notebook.
e. Turn on the power supply.
f. Observe the input and output waveforms with your oscilloscope. Sketch them
into your lab notebook. Make certain to include voltage and time dimensions.
g. Measure and record the average load voltage, 𝑉𝑑𝑐 , using the DVM. (NB: make
certain it is set on DC.)
h. Turn off the power, insert the DC milliameter, turn the power back on, and
measure and record the average load current, 𝐼𝑑𝑐 . Turn off the power, remove
the DC milliameter, and turn the power back on.
i. Measure and record the PIV (peak inverse voltage) across the diode using the
oscilloscope.
j. Measure and record the peak-to-peak value of the ripple voltage, 𝑉𝑟(𝑝−𝑝) ,
using the oscilloscope.
k. Measure and record the rms value of the ripple voltage, 𝑉𝑟(𝑟𝑚𝑠) , using the
oscilloscope.
l. Turn OFF the power supply.
5. Construct the circuit shown in Figure 7- 4 using the 100 µF electrolytic capacitor, but
replacing the 1.5 kΩ load resistor with the resistor substitution box..
a. While observing the output waveform with your oscilloscope, gradually
increase the resistance of the substitution box up to 10 MΩ which is
effectively “no load.” Sketch the “no load” wave form in your lab notebook.
b. Measure and record the average value of the load voltage, 𝑉𝑑𝑐 , at “no load”
(R = 10 MΩ).
6. Clean up your lab station and put all materials away.
Results:
1. Using the results obtained from the pre-lab calculations 7 and 8, create Error!
eference source not found..
Quantity
Unfiltered
Filtered
𝑉𝑑𝑐
𝐼𝑑𝑐
𝑃𝐼𝑉
xxxxxxxx
𝑉𝑟(𝑝−𝑝)
xxxxxxxx
𝑉𝑟(𝑟𝑚𝑠)
Table 7- 1
2. Using the results obtained from procedure steps 2 and 4 above, create Table 7- 2
Quantity
Instrument
Unfiltered
Filtered
𝑉𝑑𝑐
𝐼𝑑𝑐
𝑃𝐼𝑉
xxxxxxxx
𝑉𝑟(𝑝−𝑝)
xxxxxxxx
𝑉𝑟(𝑟𝑚𝑠)
Table 7- 2
3. Create a table to compare the calculated values in Error! Reference source not
ound. with the measured values in Table 7- 2.
4. Calculate the percent ripple and percent voltage regulation of the filtered rectifier in
procedure step 4 above
5. Create a table to compare the values obtained in pre-lab calculation 9 with the results
obtained in 4 above.
Lab Notebook:
1. Observe the output waveforms from procedure steps 3 and 4 above. Comment on the
effect of the filter capacitor on the output waveform.
2. Compare the PIV of the diode in the half-wave rectifier with and without the filter
capacitor. Discuss the reason for any changes.
3. Some textbooks give equations for filtering rectifiers which assume very small ripple
voltages. These equations assume that the period of the output waveform is much
smaller than the RC time constant for the filter. Is a “small ripple” assumption valid
for either of the circuits tested in this lab?
Lab 8: Regulators and the Zener Diode
Learning Objectives:
1. Observe the characteristics of a zener diode voltage regulator.
2. Compare the performance of the zener diode voltage regulator with the voltage
divider as power supplies.
Introduction
A regulated power supply (or regulator) provides an output DC voltage that is
constant and independent of load and supply variations. The zener diode is one of the most
common devices used to provide this regulation. The zener diode operates in the reverse, or
zener breakdown region, of the i-v characteristic curve to hold a nearly constant voltage over
a large range of currents.
Another way to provide a fixed voltage is with the voltage divider circuit. The
voltage across a resistor in series is proportional to the resistance. If the supply voltage, Vs,
and the load were constant, this would provide a fixed output voltage. However, if the
supply voltage varies then the output from the voltage divider would also vary.
Suppose a circuit is needed to provide 8.2 VDC to a load resistor, RL, in an
application where 12 VDC ± 2VDC is available (such as in an automobile). As shown in
Figure 8- 1, the circuit must receive a voltage of 12 VDC ± 2V and output a voltage of 8.2
VDC for all load resistors greater than 1 kΩ. In this lab, we will compare the voltage divider
circuit to a zener diode regulated circuit to provide the required output under supply
variations.
Figure 8- 1
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Section 7.3.
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 7.30
Required Materials:
1 – Laboratory power supply
1 – DVM
1 – Oscilloscope
1 – Prototype Bread Board
1 – Zener diode, 8.2 V, 400 mW
1 – 1 kΩ resistor, ¼ W
1 – 470 Ω resistor, ¼ W
1 – 180 Ω resistor, ¼ W
1 – Resistor substitution box
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the load voltage, VL, and current, IL, for supply voltages of 10 V, 12 V, and
14 V and for load resistances of 1 kΩ, 1.5 kΩ, 3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ for
the circuit in Figure 8- 2.
Figure 8- 2
2. Calculate the load voltage, VL, and current, IL, for supply voltages of 10 V, 12 V, and
14 V and for load resistances of 1 kΩ, 1.5 kΩ, 3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ for
the circuit in Figure 8-3.
Figure 8- 3
Procedure:
1. Construct the circuit shown in Figure 8- 2.
a. Have your lab instructor check your circuit and initial your lab notebook.
b. Set the low voltage DC power supply to 10 V, turn it off, connect it to your
circuit, and turn it on.
c. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
d. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
e. Turn off the low voltage power supply, disconnect it, set the low voltage DC
power supply to 12 V, turn it off, connect it to your circuit, and turn it on.
f. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
g. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
h. Reset the load resistance to 1 kΩ. Using the oscilloscope set for AC coupling,
measure the peak-to-peak value of the ripple voltage at the power supply and
across RL.
i. Turn off the low voltage power supply, disconnect it, set the low voltage DC
power supply to 14 V, turn it off, connect it to your circuit, and turn it on.
j. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
k. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
l. Turn off the low voltage power supply.
2. Construct the circuit shown in Figure 8- 3.
a. Have your lab instructor check your circuit and initial your lab notebook.
b. Set the low voltage DC power supply to 10 V, turn it off, connect it to your
circuit, and turn it on.
c. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
d. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
e. Turn off the low voltage power supply, disconnect it, set the low voltage DC
power supply to 12 V, turn it off, connect it to your circuit, and turn it on.
f. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
g. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
h. Reset the load resistance to 1 kΩ. Using the oscilloscope set for AC coupling,
measure the peak-to-peak value of the ripple voltage at the power supply and
across RL.
i. Turn off the low voltage power supply, disconnect it, set the low voltage DC
power supply to 14 V, turn it off, connect it to your circuit, and turn it on.
j. Measure and record the load voltage, VL, for load resistances of 1 kΩ, 1.5 kΩ,
3.3 kΩ, 4.7 kΩ, 10 kΩ, and 10 MΩ.
k. Calculate the load current, 𝐼𝐿 = 𝑉𝐿 ⁄𝑅𝐿 , for each load resistance.
l. Turn off the low voltage power supply.
3. Clean up your lab station and put all materials away.
Results:
1. Show the various results in your lab notebook from the pre-lab calculations and
procedures using Table 8-1. Make certain to label the values shown in these tables.
10 V
12 V
14 V
1 kΩ
1.5 kΩ
3.3 kΩ
4.7 kΩ
10 kΩ
10 MΩ
Table 8- 1
2. Calculate the current flowing through the zener diode when the supply voltage is
12 V and the load resistance is 1 kΩ.
3. Calculate the percent voltage regulation (refer to lab 6) for the regulator circuit
(Figure 8- 2) and the voltage divider circuit (Figure 8- 3) assuming “no load” is 𝑅𝐿 =
10MΩ and “full load” is 𝑅𝐿 = 1 kΩ.
Lab Notebook:
1. Plot VL vs IL for the input voltages of 10 V, 12 V, and 14 V for the zener diode circuit
and for the voltage divider circuit (an unregulated circuit). Plot both curves on the
same graph. You may use MatLab or plot these by hand, but the plot must be neatly
inserted into your lab notebook.
2. Compare the ripple voltages measured in step1.h and 2.2.h. Which circuit is most
effective in filtering out the ripple coming from the low-voltage DC power supply?
3. Comment on the percent voltage regulation of each circuit.
Lab 9: BJT Switching
Learning Objectives:
1. Observe the characteristics of a BJT transistor used as a switch.
2. Observe circuits using a BJT transistor switch.
Introduction
The bipolar junction transistor (BJT) is a semiconductor device similar to the diode.
The BJT either adds another p layer next to the n of the diode, making a pnp BJT; or it adds
another n layer next to the p of the diode, making an npn BJT. The latter is the most
common and is the one we will be using in this lab.
The BJT is a three terminal device (one terminal attached to each layer) that can be
used for amplification or for switching. For amplification, we operate the transistor in its
linear region. For switching, the transistor is operated in the non-linear regions.
A voltage applied to the base of a BJT can switch the output voltage. We see that
when the input voltage is high, the transistor is operating in the saturation region and the
output voltage is essentially 0. When the input voltage is low, the transistor is operating in
the cutoff region, and the output voltage is essentially VCC.
Figure 9-1 illustrates an NPN BJT used as a switch to turn on and off the current, IC,
through resistor RC. As a switch, the BJT circuit operates like the circuit shown in
Figure 9-2.
Figure 9- 1
Figure 9- 2
When +5 V is applied to Vi, IB will be approximately 160 µA. The transistor would
be in the saturation region, the switch would be closed, VCE would be approximately 0 V and
IC would be approximately 5 mA.
When 0 V is applied to Vi, IB will be 0 A. The transistor would be in the cutoff
region. The switch would be open. VCE would be 5 V and IC would be 0 A.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Section 7-4.
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 7.53
Required Materials:
1 – Laboratory power supply
1 – DVM
1 – NPN transistor
1 – 1 kΩ resistor, ¼ W
1 – 27 kΩ resistor, ¼ W
1 – 150 Ω resistor, ¼ W
1 – LED lamp
1 – 5 VDC relay
1 – Diode, 1 A, 200 V PIV
1 – Resistor substitution box
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the base current in Figure 9-1 when +5 V is applied to the input. (NB: the
answer is given above). Recall that saturation occurs when 𝐼𝐶 ⁄𝐼𝐵 < 𝛽, the
transistor’s current gain (sometimes also called hFE). In the saturated mode,
VBE ≈ 0.7 V. Therefore, we can use Ohm’s Law to calculate the base current:
5 − 0.7
𝐼𝐵 =
𝑅𝐵
2. Calculate the collector current in Figure 9-1 when +5 V is applied to the input. In the
saturated mode, VCE ≈ 0.2 V. Therefore, we can use Ohm’s Law to calculate the
collector current:
𝐼𝐶 =
5 − 0.2
𝑅𝐶
Procedure:
1. Construct the circuit shown in Figure 9-1.
a. Have your instructor check your circuit board and initial your lab notebook
before connecting the power supply.
b. Apply +5 V to the input, Vi. Measure VBE, VCE, and the voltages across RB and
RC.
c. Calculate IB and IC using the measured values.
d. Apply 0 V to the input. Measure VBE, VCE, and the voltages across RB and RC.
e. Calculate IB and IC using the measured values.
f. Turn off the power supply.
2. Construct the circuit shown in Figure 9- 3.
Figure 9- 3
a. Use the resistor substitution box for RB.
b. Have your instructor check your circuit and initial your lab notebook before
applying power.
c. Set the resistor substitution box to 47 kΩ.
d. Apply +5 V to the input, Vi.
e. Reduce the resistance setting of the substitution box until 𝑉𝐶𝐸 ≤ 0.2 V.
Record that value of RB.
f. Measure VBE, VCE, and the voltages across RB and RC.
g. Note the state of the LED.
h. Calculate IB and IC using the measured values.
i. Apply 0 V to the input. Measure VBE, VCE, and the voltages across RB and RC.
j. Note the state of the LED.
k. Calculate IB and IC using the measured values.
l. Turn off the power supply.
3. Construct the circuit in Figure 9- 4
Figure 9- 4
a. Use the resistor substitution box for RB.
b. Have your instructor check your circuit and initial your lab notebook before
applying power.
c. Set the resistor substitution box to 22 kΩ.
d. Apply +5 V to the input, Vi.
e. Reduce the resistance setting of the substitution box until 𝑉𝐶𝐸 ≤ 0.2 V.
Record that value of RB.
f. Measure VBE, VCE, and the voltages across RB and RC.
g. Note the state of the LED.
h. Calculate IB and IC using the measured values.
i. Apply 0 V to the input. Measure VBE, VCE, and the voltages across RB and RC.
j. Note the state of the LED.
k. Calculate IB and IC using the measured values.
l. Turn off the power supply.
4. Clean up your lab station and put all your material away.
Results:
1. Show the results of procedure step 1 using Table 9- 1.
Vi
VBE
IB
Switch
VCE
State
+5 V
0V
IC
Table 9- 1
2. Show the results of procedure step 2 using Table 9- 2.
Vi
VBE
IB
Lamp
VCE
State
+5 V
0V
IC
Table 9- 2
3. Show the result of procedure step 3 using Table 9- 3.
Vi
VBE
IB
Lamp
Relay
State
State
+5 V
0V
VCE
IC
Table 9- 3
Lab Notebook:
1. Calculate the ratio 𝐼𝐶 ⁄𝐼𝐵 for the data in Table 9- 1. How does this compare to the β
(or hFE) for the 2N3904? (Google 2N3904 for the data sheet.)
2. Using the data from Table 9- 2, calculate the voltage across and the current through
the LED when the transistor switch is “closed.”
3. For the lamp driver in step 2, calculate the largest value of RB which may be used so
that the lamp will be lighted. For this calculation of RB(max), use the measured value
of IB and the minimum value of β. Compare this value RB(max) with the value of RB
obtained in step 2.
4. For the relay driver in step 3, calculate the largest value of RB which may be used to
activate the relay, assuming the resistance of the coil is 125 Ω. Compare this value of
RB(max) with the value of RB obtained in step 3.
5. What is the purpose of the diode in Figure 9- 4?
Lab 10: Combinational Logic
Learning Objectives:
1. Verify the truth table of the universal NAND gate.
2. Study certain basic logic functions and applications.
Introduction
Boolean algebra (or as George Boole, who published a seminal treatise on the subject
in 1854 called it, logical algebra) deals with variables that can only take on one of two
values, 1 or 0 (True or False). Generally, the higher voltage value represents the 1 or True
state and the lower voltage value represents the 0 or False state. This is called positive logic.
It is also possible to represent the 1 or True state with the lower voltage value and the 0 or
False state with the higher value. This is called negative logic.
The basis of Boolean algebra lies in the operations of logical addition (OR), logical
multiplication (AND), and logical negation (NOT). There are two other common gates, the
NAND gate and the NOR gate. The truth table for the NAND gate is summarized in Table
10- 1.
A
B
A NAND B
0
0
1
0
1
1
1
0
1
1
1
0
Table 10- 1
The last two gates are called “universal” gates because any other gate can be
constructed using only NAND gates or only NOR gates. The 7400 (Figure 10- 1) packages
four NAND gates into a single IC chip
Figure 10- 1
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Chapter 8
Required Materials:
1 – ETS-7000, Digital-Analog Training System
1 – DVM
2 – 7400 (or 74LS00) quad 2-input NAND gates
1 – 7447 (or 74LS47) BCD – 7 Segment Converter
1 – MAN 3620 (or other common anode type) 7 Segment Display
1 – 180 Ω resistor, ¼ W
Test leads and hook-up wire
Procedure:
1. Use the ETS- 7000 to check both 7400 chips. Connect the inputs to the switches and
the outputs to the lamps. Connect pins #14 and #7 to +5V and ground, respectively.
The truth table for the NAND gate is shown in Table 10- 1 above. Be sure to verify
the truth table for each gate on each 7400 chip. Return any chips that have one or
more defective gates to the instructor.
2. Construct circuit (a) in Figure 10- 2.
Figure 10- 2
a. Copy the schematic into your lab notebook.
b. Write the pin numbers from the 7400(s) that you plan to use on the schematic
in your notebook.
c. Determine the truth table for this circuit. Record it in your lab notebook.
3. Repeat step 2 for the other three circuits in Figure 10- 2.
a. Have your lab instructor check your results and initial your lab notebook.
b. Determine the Boolean expression and the name for each of the four circuits.
4. Construct the circuit shown in Figure 10- 3.
Figure 10- 3
a. Connect each of the four switches on the ETS-7000 to the four inputs (D0,
D1, D2, and D3) of the 7447 as shown.
b. Connect the 180 Ω resistor between the common anode (C.A.) pin and VCC.
c. Use the four switches to set the input bits, DCBA, to all possible values from
0000 to 1111.
i. Record the results seen on the 7 segment display.
ii. Also, use your DVM to observe the state of the 7 outputs from the
7447 each input and record the measured values.
5. Clean up your lab station and put all the components and equipment away.
Results:
1. Show the results of procedure steps 2 and 3 using Table 10- 2.
A
B
Fx
0
0
0
1
1
0
1
1
Table 10- 2
2. Show the results of procedure step 4 using Table 10- 3
D
C
B
A
a
b
c
d
e
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1
1
f
0
g
1
Symbol
Table 10- 3
Lab Notebook:
1. The NAND gate and the NOR gate are called “universal” gates because any other
gate can be constructed only using this configuration. Show how an inverter (NOT
gate) can be constructed using only one or more NAND gates and using only one or
more NOR gates.
2. The circuits in Figure 10- 2 (a) and (d) constitute a half-adder. Explain why this is so.
3. Logic outputs are said to be “asserted” high or low depending upon which level (high
or low) is “active” (that is, produces the desired effect. Look at your truth table for
the 7447 (Table 10- 3). Are its outputs asserted high or asserted low? What about the
inputs to the 7447?
4. How do you explain the strange symbols that are displayed on the 7 segment display
when the numbers 1010, 1011, 1100, 1101, 1110, and 1111 are applied to the input
terminals DCBA?
5. Which is the most significant bit (A, B, C, or D) of the inputs to the 7447 and which
is the least significant bit? Could that be reversed? If not explain why not. If so,
explain how.
Lab 11: Sequential Logic
Learning Objectives:
1. Verify the truth table of the JK flip-flop.
2. Study some flip-flop applications.
Introduction
The output of combinational logic circuits, which were studied in the previous lab,
depend only upon the current inputs. Sequential logic circuits, which we will study in this
lab depend upon past as well as current inputs. The basic building block which converts a
logic circuit from combinational to sequential is the flip-flop.
The RS flip-flop (Reset/Set) can be constructed using combinational gates. The RS
latch (another name for the flip-flop) is also available commercially. The RS flip-flop does
not allow inputs to both the Set and the Rest terminal simultaneously. The D flip-flop and
data latch are logical extensions of the RS flip-flop. The J-K flip-flop is an extension of the
RS latch that allows simultaneous inputs. The JK latch is the device that we will be studying
in this lab. The truth table for the JK flip-flop is summarized in Table 11-1.
𝐽𝑛
𝐾𝑛
𝑄𝑛+1
0
0
𝑄𝑛
0
1
0
1
0
1
1
1
𝑄̅𝑛
Table 11- 1
The 74112 IC packages two JK flip-flops as shown in Figure 11- 1. Both flip-flops
are powered by a single source voltage which is set at +5 VDC and share the same ground.
Figure 11- 1
Pre-Lab Reading:
Zevakat, CUSTOM ENGINEERING, Chapter 8
Pre-Lab Exercises:
Zevakat, CUSTOM ENGINEERING,
Problem 8.62
Required Materials:
1 – ETS-7000, Digital-Analog Training System
1 – DVM
2 – 74112 dual JK flip-flop
1 – 7400 (or 74LS00) quad 2-input NAND gates
1 – 7447 (or 74LS47) BCD – 7 Segment Converter
1 – MAN 3620 (or other common anode type) 7 Segment Display
1 – 180 Ω resistor, ¼ W
Test leads and hook-up wire
Pre-Lab Calculations:
1. Use a logic diagram to construct a D flip-flop from a J-K flip-flop. You may use any
other combinational logic gates that you need.
Procedure:
1. Use the ETS- 7000 to check both 74112 chips. Connect the inputs to the switches
and the outputs to the lamps. Connect pins #16 and #8 to +5V and ground,
respectively. The truth table for the JK latch is shown in Table 11- 1 above. 𝑄𝑛+1 is
the output after the clock pulse. 𝑄𝑛 is the output before the clock pulse. 𝑄̅𝑛 is the
complement of 𝑄𝑛 .
a. Select one of the flip-flops for test. Connect the clock input, C, to a positive
pulse switch.
b. Connect the S input to +5V and the R input to a negative pulse switch.
(Notice that ̅̅̅̅̅̅
𝑃𝑅𝐸 and ̅̅̅̅̅̅
𝐶𝐿𝑅 in Figure 11- 1 are active low.)
c. Connect the J and K inputs and the Q and Q/ outputs to four lamps.
d. Reset the flip-flop (Q=0) by pressing the negative pulse switch connected to
the R input.
e. Copy Table 11- 2 into your lab notebook.
J
K
𝑄𝑛
𝑄𝑛+1
0
0
0
0
0
1
0
1
0
1
1
0
1
0
1
0
1
1
1
0
0
1
1
1
Table 11- 2
f. Set J and K to the first line values (0,0). Momentarily press the positive pulse
button connected to the clock. Record the value of 𝑄𝑛+1.
g. Proceed to the next line. Set J and K, clock, and record the value of 𝑄𝑛+1 .
h. Repeat step on page 52 until all eight lines are complete.
i. Ask your instructor to check your table and initial your lab notebook before
proceeding.
2. Repeat steps 1.a through 1.h for each flip-flop. Return any chips with defective flipflops to your instructor.
3. Construct the circuit shown in Figure 11- 2.
Figure 11- 2 - Two State (One Bit) Counter
a. Connect the A output to a lamp.
b. Connect the C input to a positive pulse switch. Connect the R input to a
negative pulse switch.
c. Connect the S input to VCC = +5 V.
d. Note that the Q output is connected to the K input and the Q/ output is
connected to the J input.
e. Reset the flip-flop (press the negative pulse switch connected to R).
f. Apply clock pulses and record the output to A as a timing diagram showing
the clock and the output.
4. Construct the circuit shown in Figure 11- 3.
Figure 11- 3 - Four State (Two Bit) Counter
a. Connect the A output and the B output to lamps.
b. Connect the C input of the first flip-flop to a positive pulse switch. Connect
the R input of both flip-flops to the same negative pulse switch.
c. Connect both S inputs, both J inputs, and both K inputs to VCC = +5 V.
d. Connect the Q output from the first flip-flop to the C input of the second flipflop.
e. Reset the flip-flops (press the negative pulse switch connected to R).
f. Apply clock pulses and record the output to A and the output to B as a timing
diagram showing the clock and the outputs.
5. Construct the circuit shown in Figure 11- 4.
Figure 11- 4 - Sixteen State (Four Bit) Counter
a. Connect the A output, the B output, the C output, and the D output to lamps.
b. Connect the C input (Note that this indicates the clock. It is not the same as
the C output, which simply identifies a particular Q output.) of the first flipflop to a positive pulse switch. Connect the R input of all the flip-flops to the
same negative pulse switch.
c. Connect all S inputs, all J inputs, and all K inputs to VCC = +5 V.
d. Connect the Q output of the first flip-flop to the C (clock) input of the second
input. Connect the Q output of the second flip-flop to the C (clock) input of
the third flip-flop. Connect the Q output of the third flip-flop to the C (clock)
input of the fourth flip-flop. Save the NAND gate for step 6.
e. Reset the flip-flops (press the negative pulse switch connected to R).
f. Apply clock pulses and record the output to A, the output to B, the output to
C, and the output to D as a timing diagram showing the clock and the outputs.
g. Reset the flip-flops (press the negative pulse switch connected to R) before
proceeding to step 6.
6. Replace the negative pulse switch in Figure 11- 4 with the NAND gate. Connect the
output from B to one input of the NAND gate and the output from D to the other
input.
a. Apply clock pulses and record the output to A, the output to B, the output to
C, and the output to D as a timing diagram showing the clock and the outputs.
7. Clean up your lab station and put all the components and equipment away.
Lab Notebook:
1. Explain briefly how your truth table for the J-K flip-flop, developed using
Table 11- 2, agrees with the generalized table shown in Table 11- 1.
2. In what way is the use of a J-K flip-flop less restrictive than that of an S-R flip-flop.
3. How many states, in general, does an N-bit counter have?
4. Why are the inputs of the NAND gate in Figure 11- 4 connected to the D and B
outputs?
Lab 12: Load Test of AC Induction Motors
Learning Objectives:
1. Determine the load and input characteristics of a single-phase induction motor.
2. Determine the load and input characteristics of a three-phase induction motor.
Caution: 208 VAC is used for this experiment. You must have your instructor
check your wiring before applying power at each of the steps listed. Failure to
do so could result in injury and WILL result in failure of this lab.
Introduction
The induction motor is the most widely used electric machine. Although the analysis
is somewhat difficult, the construction is surprisingly easy. The input voltage is wired in the
stator. The rotor has windings that are NOT connected to any outside source. Rather, the
AC voltage in the stator induces (hence the name) a voltage in the rotor. This induced
voltage in turn creates a magnetic field which reacts with the magnetic field created by the
stator, thus producing a torque.
An induction motor (as is true for all motors and generators) is an “energy
conversion” device. A major concern, therefore, has to do with efficiency. Efficiency is
calculated as
𝜂=
𝑃𝑜𝑢𝑡
.
𝑃𝑖𝑛
The single-phase induction motor’s torque will pulse as the supply voltage moves
through its cycle. Although this pulsing is generally unnoticeable without instrumentation
and does not cause significant problems in residential and most commercial application, the
mechanical vibrations create a greater wear on the motor and everything connected to it. The
three-phase induction motor, on the other hand, provides constant torque throughout its
operation. This property makes the three-phase induction motor the most common motor
used in industrial applications.
In this lab, we will investigate both single-phase and three-phase induction motors.
Note that we will be using 115 VAC and 208 VAC supplies. These supplies can create
dangerous and even deadly currents. A review of Appendix A at this time would be most
appropriate.
Pre-Lab Reading:
Zekavat, CUSTOM ENGINEERING, Chapter 12
Pre-Lab Exercises:
Zekavat, CUSTOM ENGINEERING,
Problem 12.40
Required Materials:
1 – Laboratory power supply
1 – ¼ HP, 115 V, 1725 RPM, single-phase induction motor
1 – ½ HP, 208 V, 1725 RPM, three-phase induction motor
1 – Multi-range AC voltmeter
1 – Multi-range AC ammeter
1 – Multi-range kilo-wattmeter
1 – Three-pole insertion switch
1 – Strobotach
1 – Pony brake and scale
Test leads and hook-up wire
Pre-Lab Calculations:
1. Calculate the synchronous speed for a 60 Hz induction motor with 2, 4, 6, and 8
poles.
2. For each motor in the Required Materials list, calculate the approximate torque
(in lb-ft) at 0%, 50%, and 100% load. Assume the motor is operating at the rated
speed.
3. For a torque arm of 2 inches (1/6 foot), calculate the force required for each torque
calculated in 2 above.
Procedure:
1. Construct the circuit shown in Figure 12- 1.
Figure 12- 1
a.
b.
c.
d.
Use one slot of the three-phase insertion switch for this circuit.
Attach the pony brake to the motor shaft.
Have your lab instructor inspect your circuit and initial your lab notebook.
Beginning with no-load, start the motor and record the voltage, current,
power, and rotor speed at 0%, 50%, and 100% of full load.
e. Remove the load and switch off the motor.
f. Reverse the input leads and switch the motor back on. Record the results.
g. Switch off the motor.
2. Construct the circuit shown in Figure 12- 2 using the three phases of the 208 V
supply.
Figure 12- 2
a. Attach the pony brake to the motor shaft.
b. Have your lab instructor inspect your circuit and initial your lab notebook.
c. Beginning with no-load, start the motor and record the voltage, current,
power, and rotor speed at 0%, 50%, and 100% of full load.
d. Remove the load and switch off the motor.
e. Reverse two input leads and switch the motor back on. Record the results.
f. Switch off the motor.
3. Clean up your lab station and put all materials away.
Results:
1. Using the data gathered in the procedures above, calculate and tabulate the torque,
slip, HP output, efficiency, and power factor for each motor at 0%, 50%, and 100% of
full load.
2. Calculate and record the ratio of the starting current to the full load current for each
motor.
3. Calculate and record the ratio of the starting torque to the full load torque for each
motor.
Lab Notebook:
1. Discuss what happened in procedure steps 1.f and 2.2.e. What is the significance of
this?
2. During the load tests, where does the energy come from? How much energy is
provided?
3. How much energy is dissipated during the load tests? Discuss all of the energy
drains, both desirable and undesirable.
Appendix A - Laboratory Safety
Safety is always a concern when working with electricity. Not only is there potential
for electric shock, the current passing through circuit elements can also generate enough heat
to cause severe burns to the skin on contact. Furthermore, if flammable material (such as
paper) comes in contact, this could result in a fire hazard.
The cause of electric shock is current passing through a person’s body. Voltage is
what causes current to flow, but even small voltages can produce enough current to kill a
person. A current as small as 0.1 A flowing through the head or the upper thorax is generally
fatal. The “let-go” threshold is only 16 mA and 9 mA will produce a painful shock.
The following rules should be observed when you work with electricity:

Always turn power off before assembling, disassembling, or reassembling any
circuit. If a circuit contains any capacitors, they should be discharged using an
insulated probe before touching any part of the circuit.

Never work alone. Know where the telephone is to call for help (911) in case of
an emergency.

Wear (preferably rubber soled) shoes and make sure they are dry. Do not stand
on wet or metal floors. Never handle any electrical equipment or circuits when
your hands are wet.

Remove rings, watches, metal necklaces, and any other metal jewelry when you
are working with circuits.

Never work with electricity if you have been drinking, when you are tired, or if
you are taking medications that make you drowsy.

Know the location of the emergency power off switch for the laboratory, the
nearest emergency alarm, the nearest AED (Automated External Defibrillator),
and the nearest emergency exit.

When taking measurements on live circuits, use insulated probes and keep one
hand behind your back. Do not touch any part of a live circuit with any part of
your body.

Wear safety glasses when appropriate. Safety glasses are especially appropriate
when soldering, when clipping lead wires, when working with electrolytic
capacitors, when working with equipment which may arc, and when working with
rotating electrical equipment such as motors and generators.

Never open the field circuit of a DC motor. This can cause dangerously high
speeds which would result in a mechanical explosion.

When working with rotating equipment, do not wear loose sleeved shirts, ties, or
any other loose clothing that could get caught in the equipment.

Never use water, class A, or class B fire extinguishers on electrical fires. Know
where the class C fire extinguisher is located in the lab. Read the instructions
now so that you would know how to use the extinguisher if needed. If an
electrical fire breaks out in the lab, turn off the power (if possible) and use the
class C fire extinguisher on the fire. Call 911.

If another person can not let go of an energized circuit, do NOT try to pull them
away. You may become a part of the circuit and also become shocked. Turn off
the power if that is possible. If it is not possible to turn off the power, try to use
any nonconductive material to separate the person from the circuit. If the
person’s heart has stopped, bring the AED to them. The AED has enough
intelligence built into it to instruct you how to use it. Call 911.

Do not use power cords that are frayed or that have missing or bent grounding
pins.

Keep your work area neat and free of clutter. Keep any stools and chairs that are
not being used under the bench to avoid tripping hazards. Keep equipment back
from the edge of the bench. If something does fall, do not try to grab it. It may
be live and electrocute you.

Never assume that a circuit is off. Check the circuit with a reliable meter before
handling.

Report any conditions that you think might be unsafe to your lab instructor.
Appendix B - Resistor Color Codes
First Color Band
Color
First Value
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Second Color Band
Color
Second Value
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Gray
8
White
9
Third Color Band
Color
Multiplier
Gold
0.1
Black
1
Brown
10
Red
100
Orange
1000
Yellow
104
Green
105
Blue
106
Violet
107
Gray
108
White
109
Table C.1 First, Second, and Third Color Bands
First and Second
Band Colors
Brown, Black
Brown, Red
Brown, Green
Brown, Gray
Red, Red
Red, Violet
Orange, Orange
Orange, White
Yellow, Violet
Green, Blue
Blue, Gray
Gray, Red
Gold
1.0
1.2
1.5
1.8
2.2
2.7
3.3
3.9
4.7
5.6
6.8
8.2
Black
10
12
15
18
22
27
33
39
47
56
68
82
Brown
100
120
150
180
220
270
330
390
470
560
680
820
Third Band Color
Red Orange Yellow
1k
10k
100k
1.2k 12k
120k
1.5k 15k
150k
1.8k 18k
180k
2.2k 22k
220k
2.7k 27k
270k
3.3k 33k
330k
3.9k 39k
390k
4.7k 47k
470k
5.6k 56k
560k
6.8k 68k
680k
8.2k 82k
820k
Table C.2 Standard Resistance Values (in Ohms) for 10% Tolerance Series
Tolerance (fourth) Band
Color
Tolerance
Red
2%
Gold
5%
Silver
10%
Tolerance band missing 20%
Table C.3 Fourth (Tolerance) Color Band
Green
1M
1.2M
1.5M
1.8M
2.2M
2.7M
3.3M
3.9M
4.7M
5.6M
6.8M
8.2M
Blue
10M
12M
15M
18M
22M
27M
33M
39M
47M
56M
68M
82M