*Notice: The numbers were purposely changed in
this example report and may not be accurate for
practical application
Lab Section X: Lab Title
(Major Specific Project)
Student Name
ECE 201-0XX
February XX, 2010
ENGR 201
Sect 0XX
Student Name
Today’s Date
Overview:
The purpose of this lab was to create and analyze a circuit that pertains to
electrical engineering and analyze the result. The experiments conducted involve a
circuit that uses a thermal resistive sensor, a motor, various resistors, and two DC power
sources. A data-logging device was used to analyze the circuit created. Software tools
such as PSpice and DataLogger 2.0 were used to display the data collected. The major
focus of this project was to analyze thermistor’s reaction to the heat dissipated off of a
motor when exceeding its maximum power ratings.
Circuits created:
The circuit to be analyzed was created using a protoboard, a 30V power supply, a
20V battery pack, a 16k ohm resistor, a 100k ohm resistor, a 120k ohm resistor and a
thermistor resistive sensor. Figure 1a shows the thermistor voltage divider circuit that
was created1.
Figure 1a: Voltage divider circuit used characterize thermal reaction of the resistive
sensor and limit voltage into the datalogger. Vo connects to in1 of the datalogger.
A power source of 30 volts was used to power the motor. Since 30 volts was too
much for the data-logging device to handle, a voltage divider was used to lower the
voltage enough for the data logger to safely operate1. Using the 1M ohm resistor and a
100k ohm resistor the calculated voltage1 of approximately 3.0V, which was an
adequate operating voltage for the data logging.
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ENGR 201
Sect 0XX
Student Name
Today’s Date
Figure 1b shows the modified circuit created for analyzing the thermistor-motor activity.
In1 of the datalogger is connected to the thermistor voltage divider, while in2 is
connected to the voltage divider in parallel with the motor.
Figure 1b: This is the modified circuit used in test 1 and 2. Using voltage dividers,
the voltage was lowered within safe operating conditions for the datalogger.
Equations used:
𝑅2
16𝑘
𝑅2
100𝑘
𝑉𝑖𝑛(𝑅1+𝑅2)  20(120𝑘+ 16𝑘) = 2.28V
𝑉𝑖𝑛(𝑅1+𝑅2)  30(1𝑀+ 100𝑘) = 3.00V
(1)
(2)
Experiments:
The thermistor and the motor were oriented so that they were close to each
other to get optimal results. Once everything was situated, the data logger was turned
on and the power sources were connected. For both tests, the power supply voltage of
the motor was slowly increased from 0 to 25 volts and back down to 0 volts during the
time that the data logger was recording the data.
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ENGR 201
Sect 0XX
Student Name
Today’s Date
Test 1:
For this test, the thermistor and motor were held against each other. The power
sources were connected and the data logger was switched on. This test lasted about a
minute and a half. The initial rise in voltage was from raising the input voltage of the 25volt power source from 0 to 25. As depicted in figure 2a, when the motor started getting
hot, the motor voltage began to slowly drop, while the thermistor voltage slowly started
to rise. At about 55 seconds into the test, the motor was too hot to hold anymore. The
motor was then placed back on the table while the thermistor still was near it. The main
input voltage was then lowered to 0 volts and the logger was turned off after a few
seconds.
Results & Analysis:
As expected, there was a change in voltage when the thermistor heated up.
Since the data logger was connected between the 16k ohm resistor and the
thermistor, there was a voltage division. While the thermistor temperature
steadily rose, the resistance became lower. Since the thermistor was the upper
part of a voltage divider the decrease in resistance lowered the total voltage, but
raised the thermistor voltage1. As the thermistor cooled, the resistance began to
rise and the voltage lowered back to the initial voltage. A line graph of the
thermistor and motor voltage over the span of the test is displayed in figure 2a.
Data Analysis: Test One
18
16
Voltage (volts)
14
12
V
O 10
L
T 8
A
G
E 6
(V)
Motor
Thermistor
4
2
81.4
77
79.2
74.8
72.6
70.4
66
68.2
63.8
61.6
59.4
55
57.2
52.8
50.6
48.4
44
46.2
41.8
39.6
37.4
33
35.2
30.8
28.6
26.4
22
24.2
19.8
17.6
15.4
11
13.2
8.8
6.6
4.4
0
2.2
0
Time (seconds)
Figure 2a: This is a graph of the voltage of the thermistor and motor over roughly a
minute and a half.
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ENGR 201
Sect 0XX
Student Name
Today’s Date
Test 2:
During this test, the main input voltage was raised from 0 to 25 volts more slowly
than the first test, with a brief pause midway. The motor and thermistor were placed
close to each other, but were not held together this time. A little after a minute and a
half, the main input voltage was gradually turn from 25 to 0 volts. After a few seconds,
the data logger was turned off. Figure 2b shows the graph of test 2.
Results & Analysis:
There was a much slower change in voltage of the thermistor this time.
This is probably due to the reduction of the overall heater coming from the
motor. There seems to be a dip in the voltage of the motor, as was to be
expected, but towards the end, it seemed to have slightly increased. This was
due to the realization that the maximum current had been lowered between
tests, so it was set back to its original position. Since it positions of the
thermistor and motor were not changed this time, the thermistor did not cool
down at the end because the motor was still emitting heat.
Data Analysis: Test Two
16
14
Voltage (volts)
12
V
O
L
T
A
G
E
(V)
10
Motor
8
Thermistor
6
4
2
119
116
112
109
105
102
98.6
95.2
91.8
85
88.4
81.6
78.2
74.8
68
71.4
64.6
61.2
57.8
51
54.4
47.6
44.2
40.8
34
37.4
30.6
27.2
23.8
17
20.4
13.6
6.8
10.2
0
3.4
0
Time (seconds)
Figure 2b: This is a graph of the voltage of the thermistor and motor over a span of 2m..
Lab Questions:
Be sure to add all lab questions in to your report.
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ENGR 201
Sect 0XX
Student Name
Today’s Date
Challenge Qustion:
Challenge questions should be in their own section. Be sure to treat challenge
problems like and experiment (adding schematics, graphs, tables, etc)
Conclusion:
While using a thermistor and a motor, this lab showed the thermistor resistance
lowers when the motor heats up, while raising its own voltage. When manipulated
correctly, the thermistor could regulate how much power goes to the motor and
theoretically prevent it from overheating.
See attached for raw data collected from the data-logging device.
Page 6