LAB2 – Resistors, Simple Resistive Circuits in Series and Parallel
Objective: In this lab, you will become familiar with resistors and potentiometers and will learn
how to measure resistance. You will also familiarize yourself with series and parallel DC
circuits and you will verify fundamental circuit properties. Using simple sensors, you will
convert nonelectrical parameters (light intensity) to electrical resistance. You will use the
breadboard on the CY3214 evaluation board and your digital multimeter for this lab.
Items needed:
CY3214 eval board
Wire package
Digital Multimeter with probes Radio-Shack #22-810
*12V battery for digital multimeter Radio-Shack #23-144
*Phillips type screwdriver to install battery into multimeter
*Test clip adapters for digital multimeter Radio-Shack #270-334B
9-volt battery Radio-Shack #23-875
9-volt battery snap connector Radio-Shack #270-324 (has 5 connectors in pkg)
Package of resistors Radio-Shack #271-308
The Breadboard
A breadboard is used for holding logic chips, components, and wires that connect them together in order
to realize a desired circuit. Breadboards allow engineers to try out circuits without having to solder them
to a printed circuit board. The breadboard on the CY3214-PSoCEval-USB board has 400 pin holes in it.
The holes are arranged with 0.1” separation between them in a grid pattern.
Note there are 30 rows with columns labeled a-j. For each row, the five holes in columns a-e are
connected in common. Likewise, the five holes in columns f-j are connected in common. What is
meant by common connections is that a row or column of common pins will have the same voltage as
each other (or same logic state). This common connection will allow multiple connections to be made at
the same pin on a logic chip or allow a node of a circuit to be made. On each side of the rows are two
columns, one with red marking and one with blue marking. All of the pins in each column are
commonly connected. These columns are often used for providing supply power and ground to the
nodes of a circuit.
To show the connectivity between holes that are
commonly connected, take two precut and stripped
wires (the standard size - #22 or #24 gauge wire)
and place them in two holes in the same row of the
breadboard. Make certain the wires are placed
securely into the holes.
Using your multimeter, measure the resistivity between each of the wires. Turn on your multimeter,
place the multimeter settings switch to Ohms (Ω), and use the lowest value setting (200); place the red
probe of the multimeter to the wired end of one wire and the black probe to the wired end of the other
wire. Using the test clips on the ends of the probes allows you to measure the values hands-free. The
value should be close to 0.0Ω if the two wires are connected together. If an open circuit is present or if
the measured resistance is higher than the range set on the multimeter, OL is shown on the multimeter
screen.
Rcommon_connection= ___________________________
Repeat the procedure but place one of the wires in a different row.
Ropen_connection = ________________________
Note: Do NOT place wires with larger diameters into the holes (Do NOT try to force the multimeter
probes into the holes) – this may damage the connections. Do NOT use stranded wire in the holes.
Linear Resistors and Resistance Measurements Resistors limit the amount of flow of electricity to a load preventing overloading.
Obtain a two resistors from the resistor package in the lab. Make certain the color bands for the two
resistors are not the same. Access a resistor color code chart from the internet and determine the values
of the resistors you have chosen.
R1color-bands=_______________
R2color-bands=____________________
R1expected = ________________
R2expected = _____________________
R1tolerance = ________________
R2 tolerance = _____________________
Place the resistors in holes that are not commonly
connected on the breadboard. Using the multimeter, place
the red probe on one end of one resistor and the black
probe on the other end. Measure the resistance.
Resistors do not have a polarity so it doesn’t matter which
side of the resistor has the red or black probe. Repeat for
the second resistor.
Record the resistance of each resistor below. How
different in percentage is the expected value from the
measured value for each resistor? Is this difference
within the specified tolerance for this resistor?
R1measured = ____________________
R2measured = ____________________________
R1%_difference = ____________________
R2%_difference = __________________________
Are these resistors ¼ watt resistors or ½ watt resistors? The power dissipated on a resistor is determined
by the equation: P = vi = v2/R = i2R. Determine the maximum voltage possible to not overpower the
smallest resistor you have.
Pmax= __________________
R = ____________________
Vmax = ________________
Resistors in Series
When two resistors are placed in series in a circuit, the equivalent resistance is the sum of the individual
resistances. Place your two resistors in series on the breadboard by placing one end of each resistor in
commonly connected holes, and measure the equivalent resistance by placing the red and black probes
on the other two ends of the resistors.
Requivalent(expected)= R1 + R2 = ___________ Requivalent(measured)=__________________
Resistors in Parallel
When two resistors are placed in parallel in a circuit, the reciprocal of the equivalent resistance is the
sum of the reciprocal of the individual resistances. For two resistors in parallel, the equation is
Requivalent =
ሺோଵ‫כ‬ோଶሻ
ሺோଵାோଶሻ
Place your two resistors in parallel on the breadboard by
placing both ends of the resistors in commonly connected
holes, and measure the equivalent resistance.
Requivalent(expected)=________________ __
Requivalent(measured)=__________________
A Series Circuit
Create a circuit using a nine-volt battery and the two resistors placed in series.
R1
V1
9V
V3
V2
R2
0
Attach a nine-volt battery to the circuit and measure each
of of the voltages, v1, v2, and v3. To measure the voltages,
pl place the multimeter with the volts setting selected across
ea each of the resistors. Verify that the three voltages satisfy
Ki Kirchoff’s voltage law (KVL: The sum of the voltages
ar around any closed loop equals zero).
V1measured = _________________
V2measured=_________________
V3measured=_______
Using Ohms Law (V=IR), calculate the expected currents across reach of the resistors.
I1calculated=__________________
I2calculated=________________
Measuring Current
When measuring current, the meter MUST be placed in series in the circuit. Do NOT place it in
parallel with the components. You will blow the fuse on the meter.
Measure the current for each path in the series circuit. Does it verify KCL (KCL:The sum of the
currents going into a node equals the sum of the currents going out of the node)?
I1measured = _________________
I2measured=_________________
V1
9V
R1
V2
I3measured=_____________
R2
V3
0
Measure the current for each path in the parallel circuit. Does it verify KCL (KCL:The sum of the
currents going into a node equals the sum of the currents going out of the node)?
I1measured = _________________
I2measured=_________________
I3measured=_____________
Voltage Divider Circuits
A common term in circuits is a voltage divider circuit. This type of circuit divides the supply voltage by
some ratio by using two resistors in series. It doesn’t really change the value of the supply voltage –
just the value of the voltage across R2 as the final voltage. Using your series resistive circuit above,
determine how much you divided the supply voltage.
V = V3 x
ோଶ
ோଵାோଶ
= __________________________
Lab Report Requirements
Copy your results from this portion of the lab into an Excel spreadsheet. Copy the results into your
report.
Use Orcad Capture CIS (part of the PSpice package) to draw the series circuit. Create a simulation and
make a screenshot of the results. Repeat this with the parallel circuit. Do the simulated results compare
with the actual or calculated results? If there are differences, explain what has caused the differences.