ENGR 43
Lab Activity
Student Guide
LAB 2 – Voltage, Current, and Resistance Measurements
Student Name: ___________________________________________________
Overview
Learning Outcomes For Activity
In this lab activity, you will make voltage,
current, and resistance measurements on the
BOE-bot robot trainer. You will compare
your measurements to specifications and
determine if your BOE-bot is ready for its
run on the racetrack. You will monitor its
operation on the track and evaluate its
performance based on your measurements
and manufacture’s data.
Relevant knowledge (K), skill (S), or
attitude (A) student learning outcomes
Before Starting This Activity
K3. Evaluate voltage of a series battery
Review the following online learning
modules on the Wisc-Online website
(www.wisc-online.com):
 Introduction to the Digital
Multimeter
 Voltmeter Circuit Connections
 Ammeter Circuit Connections
 Ohmmeter Measurements
Links to these learning modules are on the
GoogleDocs listing
(http://tinyurl.com/engr43-lablinks).
S1. Measure voltages with a DMM in a
functioning system
K1. Identify the proper meter connections
and circuit conditions for measuring
voltage, current, and resistance with a
digital multimeter (DMM)
K2. Compare measured data with specified
limits
S2. Measure current with a DMM in a
functioning system
S3. Measure resistance of components
from a deactivated system
S4. Compile data into a test report.
A1. Recognize the positive impact of wellorganized and neatly prepared report.
Time Needed
Lab Performance:
It should take students approximately 2.0
hours to work through the entire lab.
Lab Deliverables:
It should take students approximately 2.0
hours of homework time to create the lab
report summary.
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Lab Activity
Student Guide
Introduction
Equipment & Supplies
Item
BOE-bot robot trainer
Optical sensor course
tracking board
DMM and test leads
BOE-bot power monitor test
cable
AA alkaline cells (batteries) –
installed in BOE-bot
You are the technician responsible for
preparing the BOE-bot for the “ESYS 500
Robo-Race.” You will verify that the robot
is ready to race by comparing your
measurements with specified limits and you
will monitor the performance as it runs the
test course. Your final report will evaluate
the race performance and predict the
chances of your robot completing a longer
endurance race.
Quantity
1
1
2
1
4
Special Safety Requirements


Task #1 – Battery Voltage
Measurements
The BOE-bot wheels can present a
pinch hazard when moving. Keep
fingers and loose parts away from
the wheels.
Incorrect connection of an ammeter
can create a shorting hazard, with
possible overheating and damage to
the BOE-bot and meter. Ask the
instructor to double-check your
connections before connecting power
to the BOE-bot
Follow the steps to measure the individual
cell voltages and battery output voltage.
4. Download the lab worksheet
E50lab2.xlsx from the Blackboard site.
Open the file in Excel.
5. Place the BOE-bot upside-down on the
lab bench, with the rear ball wheel
facing left. If AA cells are not already in
place, install 4 cells in the battery holder.
Refer to Figure 1.
Lab Preparation
1. The lab instructor will set up the
BOE-bot racetrack for the final
performance test.
2. The BOE-bot must have the program
follow-line.bs2 loaded on the BASIC
Stamp microcontroller. The
instructor will confirm that you have
the correct software loaded.
3. The BOE-bot must have the optical
sensor course tracking board
installed. Verify that the board is
mounted securely on the front of the
robot.
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Figure 1
6. Set the DMM to measure voltage, and if
it is not an auto-ranging meter, set the
range to the closest value greater than 10
V. Measure the voltages where cell
terminals contact the battery holder.
Refer to Table 1 on the worksheet and
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Lab Activity
Student Guide
Figure 1 above for the locations of the
red (+), and black (-) leads. Enter your
measured values in Table 1. You may
round your values to the nearest
hundredth of a volt (example: round
1.325 to 1.33 volts). Take turns with all
your lab partners so that everyone makes
several voltage measurements.
7. As you enter the values in Table 1, the
values in the green cells are copied into
Table 2. Compare these values to the
minimum specified voltage. If any of the
cells are out of spec, ask the instructor
for a replacement AA alkaline cell. Once
all cells are in-spec, proceed to the next
step.
8. Turn the BOE-bot right side up, unplug
the power plug from the power jack
(labeled 6-9VDC). Measure the voltage
between the center contact and outer ring
of the power plug. Refer to Figure 2.
Determine the polarity (+ or -) of the
center contact relative to the outer ring.
Enter your findings in the area to the
right of Table 2.
sockets as shown in Figure 3. Leave the
other ends of the wires connected to the
proto-board. Connect an additional 22
AWG solid wire to the same row as the
black wires on the proto-board.
2. Set the DMM to resistance mode, and if
the meter is not auto-ranging set the
range to 200 k ohm (or higher). Place the
black meter leads on the black lead of
the opto sensor board harness and the
red meter lead on the red wire. Place
your finger over the face of the left
photoresistor and measure the “dark
resistance.” Enter the value in Table 3.
Remove your finger, measure the “light
resistance,” and enter the value in Table
3. Move the red meter lead to the green
wire. Repeat dark and light
measurements for the right photoresistor.
Figure 2
Task #2 –Resistance Measurement
Figure 3
The “eyes” of the robot are light-sensitive
resistors. We will verify that the robot can
“see” by measuring the resistance.
1. Remove the green and red jumper wires
from the “P3” and “P6” connector
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Lab Activity
Student Guide
Figure 4
Task #3 –Current and Voltage
Measurements
switch to position 2 (microcontroller and
motor power on). Both main wheels
should spin. Measure voltage and current
and enter the values in Table 4.
4. Turn the BOE-bot so that the photoresistors are pointing towards a light. Put
your finger on the face of the left photoresistor. The left wheel should stop
spinning. Take your finger off the photoresistor. The left wheel should start
spinning. Repeat for the right photoresistor and wheel. Congratulations! By
completing these steps you have verified
that the power supply, motors, and
control systems are ready for the race
track.
5. Set the power switch to 0 (OFF). With
the power monitor test cable, voltmeter,
and ammeter still connected, carefully
transport the BOE-bot to the race track.
6. Place the BOE-bot with the photoresistors straddling the black course line.
Route the cable from the test cable so
that it will not interfere with the path of
the robot on the track.
Follow the instructions carefully! Ask the
instructor to check your connections before
connecting the battery pack power plug to
the Power Test Cable!
1. Connect the BOE-bot power monitor test
cable to the power jack on the circuit
board. Do not connect the power plug
from the battery pack until instructor
checks your connections! Set one meter
to measure voltage and the other to
measure current. Connect the meters as
shown in Figure 4.
2. After the instructor has checked your
connections, plug in the power plug.
With the power switch on the BOE-bot
in position 0 (off), measure voltage and
current and enter the values in Table 4.
Set the power switch to position 1
(microcontroller on, motors off),
measure voltage and current and enter
the values in Table 4.
3. Pick up the BOE-bot so that the main
wheels can spin freely. Set the power
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Lab Activity
Student Guide
7. Set the power switch to position 2. After
one second your robot will start on the
course. Measure the voltage and current
when your robot is on one of the
straight-aways. Enter your values in
Table 4. Pick up your robot and set the
power switch to position 1.
8. The instructor will place the track on an
incline. Run your BOE-bot on the
course, and measure the voltage and
current when the robot is going uphill
and downhill, and enter these values in
Table 4.
9. In this system, the AA batteries are the
power source and the BOE-bot
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electronics and motors are the load. We
can calculate the total resistance of the
load by dividing the current into the
voltage, R = V / I. When you divide
volts by milliamps, the resistance is in
kilohms (k ohm). Calculate the
resistance for the 5 conditions listed in
Table 4.
Deliverable(s)
Save your completed Lab 2 Worksheet and
your Performance Report (at the end of this
document) in your Lab Activity Binder.
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Lab Activity
Student Guide
Lab 2 BOE-bot Performance Report
Student Name: ___________________________________________________
Battery Voltage Measurements
What can you conclude about the relation between the individual battery voltages and the total
voltage supplied to the BOE-bot?
Refer to the voltage measurement table on your lab worksheet. Can you match the position of
each battery (identified by the letters at each terminal) with the schematic of the battery pack?
What would happen if one of the AA cells were installed backwards?
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Lab Activity
Student Guide
Photo-Resistor Test
Can you positively determine if the photo-resistor is working properly from the test you
performed? What conditions, other than the photo-resistor itself, may affect the measured values
you recorded?
Voltage and Current Measurements
What is the difference between how the voltmeter and the ammeter are connected in the test
circuit? What would happen to the circuits and to the meters if the ammeter and voltmeters
swapped positions (that is, if the ammeter were connected as a voltmeter and the voltmeter were
connected as an ammeter)?
Why was it not possible to calculate the resistance for the power switch in the 0 position?
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Lab Activity
Student Guide
How did the voltage and current change for the different test conditions?
If the capacity of the AA battery pack is 1 AH (1,000 mAH), how long would the Boe-Bot run
on a straight course? Use the formula: Endurance = mAH ÷ mA
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