CleveLabs Laboratory Course System – Student Edition
Breadboard Circuit Design Laboratory
Breadboard Circuit Design
Laboratory
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Breadboard Circuit Design Laboratory
Introduction
Signal generators are electrical instruments that generate repeating electronic signals. These
signals are useful for testing, troubleshooting, and repairing electronic devices. Many common
signals are triangle, saw-tooth, sine and square wave. An example of how these signals are used
to test a circuit is shown in Figure 1. A signal sine wave is input into an amplifier circuit, and
from here an engineer can observe the output of the circuit on the oscilloscope. The amplifier
circuit should provide a gain to the known sine wave signal. Any distortion on the output besides
the signal being amplified can inform the engineer that something is wrong with the amplifier
circuit.
Signals generators are also extremely useful in communication devices such as a radio or
medical telemetry system. For example, a sine wave can be use as carrier signal in the
modulation of a signal on the transmitter side of the radio system. The sine wave carrier is then
demodulated on the receiver side of the radio system.
Figure 1: Sine wave signal input to an amplifier and output to an oscilloscope.
For this laboratory session, a breadboard will be needed. A breadboard is a thin white board on
which a prototype circuit with numerous connections for circuit elements is constructed. Figure
2 is an example of a typical breadboard layout. The top and bottom row are linked (electrically
shorted together) horizontally across, and typically used as the power supply. A battery + and –
terminal can be connected to these holes and it would be linked horizontally across. The other
holes are electrical shorted together vertically in blocks of 5, with no link across. A center gap
on the breadboard allows you to place integrated circuits (ICs) such as transistors, operational
amplifiers or timing components onto the board.
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Figure 2: A layout of a typical breadboard.
In previous laboratories, the Test Pak was used to generate a 10Hz square wave into the
BioRadio 150. In this laboratory, different components such as resistors, capacitors, and
operational amplifiers (op-amps) will be used to build a signal generator. The signals can then
be input into the BioRadio 150 and observed in the laboratory course software.
Equipment Required:
• CleveLabs Kit
• CleveLabs Course Software
• Breadboard Circuit Design Kit
• Multi-Meter
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Background
Square and Triangle Wave Oscillator
The signals that will be generated in this laboratory session are a square, a triangle and a sine
wave. These signals can be generated using two different circuits. The circuit shown in Figure
3 will be used to generate a square and a triangle wave. A square wave will be generated first.
After successfully achieving the square wave, you will add an integrator to the circuit that will
integrate the square wave signal, and as a result, produce a triangle wave at the output of the
integrator.
Square Wave Output
C1
2
1
U1
1
OUT
0
Virtual
Ground
R3
U2
2
-
+
OUT
+
OPAMP
1
1
Triangle Wave Output
R1
R2
OPAMP
2
0
Virtual
Ground
2
Figure 3: Square and triangle wave oscillator
Equation 1 specifies a square/triangle wave oscillator at a particular desired frequency. The
desired frequency depends on the components of the circuit, particularly the resistors and the
capacitors. Equation 1 determines the component values of your circuit to generate the desired
frequency of your waveform.
F =[
R
1
]x( 1 )
4 R3 C1 R2
Equation 1
Wien Bridge Oscillator
A Wien Bridge Oscillator is shown in Figure 4. A Wien Bridge Oscillator is a typical circuit
used to generate a sine wave. This circuit consists of a few resistors, capacitors and an
operational amplifier.
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Figure 4: Wien Bridge Oscillator
The circuit layout of the Wien Bridge Oscillator can be assembled as shown in Figure 5. This
layout can easily be implemented on a breadboard using electronic components. Equation 2 will
determine the frequency of the sine wave that is generated. Equation 2 should be used to design
the sine wave to the desired frequency by selecting the appropriate component values.
R2
C2
0.1uF
U1
+
Sine Wave Output
OUT
R1
C3
-
OPAMP
0.1uF
R3
0
Virtual Ground
0
Virtual Ground
R4
0
Virtual Ground
Figure 5: Wien Bridge Oscillator
f0 =
1
2π R1C1 R2 C 2
Equation 2
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If the values of the resistors are R1 = R2 = R and the values of the capacitors are C1 = C 2 = C ,
then the equation can be simplified to Equation 3. The value of R3 must be 2 times greater than
R4 to provide sufficient loop gain for the circuit to oscillate.
f0 =
R
1
with 3 = 2
R4
2πRC
Equation 3
Experimental Methods
Experimental Setup
In this laboratory, various components such as resistors, op-amps, and capacitors, will be used to
build different circuits that will generate useful output signals. First you will build up the signal
generator circuits on the breadboard using the electrical components provided in your breadboard
design kit. Next you will connect the output of your breadboard circuit to the input of your
BioRadio so that your signal can be observed in the CleveLabs software interface.
Breadboard Power Supply
The power supply used in this laboratory is a 9V battery. The op-amp, however, requires a
dual-voltage supply. This means that one pin, the +V pin, on the op-amp must be connected to a
4.5V input and another pin, the –V pin, must be connected to a -4.5 input. To create the dual
power supply we will first setup a voltage divider circuit:
Note: The inputs between A and E of each row are shorted together. The inputs between F and I
of each row are also shorted together, but are not connected to A-E.
1. Figures 6 and 7 shows the connection on the breadboard required to split the voltage of the
9V battery to act as a dual-voltage power supply.
2. Connect a 10K resistor between the red terminal (Va) and row 1 of the breadboard in a hole
between A and E. Also connect the red side of the 9V battery connector to this terminal.
3. Connect another 10K resistor between the black terminal (ground) and row 1 of the
breadboard in a hold between F and J. Also connect the black side of the 9V battery
connector to this terminal.
4. Now connect a jumper wire between row 1 (A-E) and row 1 (F-I) to complete the voltage
divider circuit.
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5. This row is the virtual ground in your circuit. You will need to connect other parts of the
circuit to virtual ground as we build it. Therefore, to allow more room for connections,
connect a jumper between an open spot on row 1 to somewhere on row 3. Then jumper
sections A-E and F-I together on row 3. This makes row 3 also your virtual ground and
provides many places to connect to as you build your circuit.
6. Now connect a jumper wire from the red terminal (Va) to one of the slots on the red +
column of the breadboard circuit. This will allow you to tap into a + 4.5 volt supply the
entire +V column down when measured against the virtual ground.
7. Now connect a jumper wire from the black terminal (ground) to one of the slots on the blue column of the breadboard circuit. This will allow you to tap into a - 4.5 volt supply the entire
-V column down when measured against the virtual ground.
Figure 6: Dual-voltage power supply using 9V battery
Figure 7: Dual-voltage power supply on a breadboard.
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Procedure and Data Collection
Square and Triangle Wave
The first circuits will be a square and triangle wave oscillator shown in Figure 9.
1. Place two op-amps on the center gap of the breadboard. Figure 8 shows the pin layout of
an LM741 Operational Amplifier. For convenience, the first should be placed such that
there are about 5 empty rows between it and the virtual ground row. The second op-amp
should be placed about 5 rows below that one.
2. Connect the V+ to pin 7 and V- to pin 4 of each op-amp to provide power. Don’t connect
the 9V battery yet, as this will be done later after the circuit is complete. To do this, you
can connect a jumper from the + column which provides the +4.5V supply to each opamp pin 7 and a jumper from the – column which provides the -4.5V supply to each opamp pin 4.
3. Use the following components, R1 = 19.5K Ohms, R2 = 10.5K Ohms, R3 = 232K Ohms,
R4=232K Ohms, and C1 = 0.1uF, to connect the circuit shown in Figure 9.
4. The op-amp non-inverting (+) is pin 3 and inverting (-) is pin 2. All virtual grounds
should be connected to the virtual ground created by the dual-voltage power supply
(between R1 and R2 of the dual-voltage power supply).
5. The first op-amp will generate a square wave at its output, while the second op-amp will
generate a triangle wave.
Figure 8: LM741 operational
amplifier pin layout
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6. The voltage at the output of the op-amp is higher than the maximum input specifications
of the BioRadio. Therefore, the voltage output needs to be decreased by setting up a
voltage divider.
7. A voltage divider needs to be set up for the square wave output and for a triangle wave
output. The output voltage of the square wave is +/- 4V. This needs to be reduced to less
than +/- 100mV. The voltage divider should consist of a R5=102K Ohms and R6=100
Ohms resistor. Figure 10 shows the connection to be made between the output of the
square wave generator and the voltage divider.
Square Wave Output
R5
R6
102K
100
0
Virtual Ground
C1
1
U1
1
OUT
Virtual
Ground
R3
232K
+
0
2
0.1µF
2
U2
R4
232K
OUT
+
OPAMP
1
R1
2
R2
OPAMP
0
Virtual Ground
19.5K
1
Triangle Wave Output
2
10.5K
Figure 9: Output of square wave oscillator through voltage divider.
Component
R1
R2
R3
R4
R5
R6
C1
Value
19.5KOhm
10.5KOhm
232KOhms
232KOhms
102KOhm
100Ohm
0.1uF
Table 1. Electronic component values for original 10 Hz square wave shown in Fig 9.
8. Now connect the 9V battery snap connection to the battery terminals.
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9. Using the alligator clip lead, connect the output of the square wave signal generator from
the breadboard to the channel 1 input of the BioRadio as shown in Figure 10.
10. On the BioRadio, connect a jumper between the blue GND input and the -1 input.
11. Using the alligator clip lead, connect the virtual ground of the circuit to the input of the
jumper on the blue BioRadio GND input.
Figure 10: Electrical connection between the BioRadio and breadboard circuit.
12. Turn the BioRadio On.
13. Start the CleveLabs software interface and enter the “Breadboard Circuit Design
Laboratory” session under the “Engineering Basics” subheading.
14. Click on the green “Start” button. The BioRadio will be automatically programmed to the
“LabBreadboardDesign” configuration when you start the lab session.
15. A square wave should be scrolling across the graph at a 3500 uV peak (7000 uV PeakPeak). Click on the Spectral Analysis tab to verify the circuit is operating at a frequency
of approximately 10Hz. Change the data collection interval to 300ms to improve the
resolution of the FFT.
16. To change the amplitude of the square wave signal, disconnect the alligator clip from the
output. The amplitude of the output can be changed by adjusting the value of resistor
value R6 of the voltage divider to a larger value. Change R6 to 1K and re-connect the
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alligator lead to the output of the circuit. Notice that the amplitude of the square wave is
now 70000uV (Peak-Peak). Click the Spectral Analysis tab. Notice that the frequency of
the square wave is still at 10Hz.
17. To change the frequency of the square wave, disconnect the alligator lead from the output
of the square wave. Change R6 of the voltage divider back to 100 Ohms. To increase the
frequency of the square wave to 50Hz, decrease the value over R3 and R4. Replace R3
and R4, each with a value of 232K Ohms, to a 93 KOhms resistor. After the changes have
been made, re-connect the alligator lead back to the output.
18. Notice the change in the waveform as the square wave scrolls across at 70000uV (PeakPeak). Click on the Spectral Analysis tab to observe the new frequency of the square
wave waveform. Since the frequency is above 10, the range of the frequency needs to be
changed to 100Hz. Notice that the frequency of this waveform is around 50Hz. The
frequency can be increased again to 100Hz by repeating this step, and replacing R3 and
R4 to a 47.5 KOhms resistor.
19. You will now observe the second output of the circuit you have created. Disconnect the
alligator clip lead from the output of the square wave. Change the resistor R3 and R4
back to 232K Ohms each. Wire the output of the second Op Amp to a circuit divider
consisting of R5=102K Ohms and R6=1K Ohms resistor. Figure 11 shows this setup.
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Triangle Wave Output
R5
102 K
C1
1
R6
1K
2
0
Virtual Ground
0.1µF
U1
1
OUT
232 K
+
0
Virtual
Ground
R3
2 1
R4
U2
2
-
232 K
OUT
+
OPAMP
1
R1
2
R2
0
Virtual
Ground
19.5K
1
OPAMP
2
10.5K
Figure 11: Setup of Triangle Wave Oscillator
Component
R1
R2
R3
R4
R5
R6
C1
Value
19.5KOhm
10.5KOhm
232KOhms
232KOhms
102KOhm
1KOhm
0.1uF
Table 2. Electronic component values for original 10 Hz square wave shown in Figure 11.
20. Now observe the output of the triangle wave circuit. Connect the alligator clip lead to the
output of the triangle wave output. Observe the signal on the CleveLabs software
interface. Notice a triangle wave scrolling across the screen with 36000uV Peak-Peak.
Click on the Spectral Analysis tab. The frequency should be around 10 Hz.
21. Disconnect the alligator lead from the output of the triangle wave output. Increase the
amplitude of the waveform by increasing R5 of the voltage divider circuit. Change R5
from 1K to 2.17K and re-connect the alligator lead to the output of the triangle wave
circuit. The amplitude of the triangle waveform should immediately change to 80000uV
peak-peak. The frequency should still be 10 Hz in the Spectral Analysis Tab.
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22. Disconnect the alligator lead from the output of the triangle wave output. Change the
value of resistor R5 of the voltage divider network back to 1KOhms. Now change the
triangle waveform to a frequency of 50Hz. To do this, simply change resistor R3 from
462K Ohms to 93K Ohms. Re-connect the alligator clip lead back to the output of the
triangle output.
23. Note the change of the waveform as the frequency increases. On the Spectral Analysis
tab, increase the frequency range from 0Hz to 100Hz. The frequency of this circuit has
increased to 50Hz. To increase the frequency to 100 Hz, repeat this step and change R3
to 47K Ohms. The amplitude can be changed by increasing resistor R5 to 2.17k Ohms.
Sine Wave
To set up the sine wave oscillator:
1. Disconnect the circuit previously set up, but leave the dual-voltage supply intact.
Disconnect the snap connector from the 9V battery.
2. Figure 13 shows the Wien Bridge Oscillator circuit. Place the 741 op-amps onto the
breadboard and connect the battery terminal V+ to pin 7 and V- to pin 4. Figure 8 shows
the pin layout of the 741 op-amps.
3. The first sine wave should have a frequency of approximately 8 Hz and 28000uV PeakPeak. Connect the circuit shown in Figure 12. The components should equal
C1=C2=0.1uF, R1=R2=163K Ohms, R3=26K Ohms, R4= 10 KOhms. The output of the
op-amp (pin 6) is connected to a voltage divider network, consisting of R5 = 102K and
R6 = 550 Ohms to limit the voltage to the range of the BioRadio 150. All virtual grounds
need to be connected to the virtual ground created by the dual-voltage power supply.
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R2
C2
Sine Wave Output
0.1uF
163 K
R5
U1
102 K
+
R1
-
163 K
550
0
Virtual Ground
OUT
C1
R6
OPAMP
0.1uF
R3
0
0
26 K
Virtual Ground Virtual Ground
R4 10 K
0
Virtual Ground
Figure 12: Wien Bridge Oscillator Circuit
4. Connect the 9V battery to the battery snap connector. The software should be running
and the BioRadio 150 should be ON. Connect -Channel 1 of the BioRadio 150 to the
virtual ground of your circuit board and connect +Channel 1 to the output of the sine
wave output, which is the point between Resistors R4 and R5. The software interface
should show a sine wave with amplitude around 28000 uV Peak-Peak. Note that the
frequency of this sine wave is around 8Hz.
5. Disconnect the output of the circuit from the BioRadio 150. To increase the amplitude of
the sine wave, the value of resistor R6 can be increased. To increase the amplitude of the
sine wave from 28000uV peak-peak to 55000uV peak-peak, simply change resistor R6
from 550 Ohms to 1KOhms. Once this is complete, re-connect +Channel 1 to the output
(Between R5 & R6) of the circuit. The amplitude of the sine wave now is around
55000uV peak-peak. Click on the Spectral Analysis tab, and note that the frequency
remains the same. Disconnect +Channel 1 from the circuit and change the value of
resistor R6 back to 550 Ohms.
6. To increase the frequency of the sine wave of the Wien Bridge Oscillator, decrease
resistor R2 and R2. The output of the BioRadio 150 should be disconnected from the
output terminal of the circuit. Replace R1 and R2 with two 32K Ohms resistors to
increase the frequency to 40 Hz. Re-connect the alligator clip lead from +Channel 1 to
the output of the circuit (Between R5 & R6).
7. A much faster sine wave should be scrolling across the screen. Since the frequency of
the sine wave increased, increase the range of the frequency in FFT Analysis from 0Hz to
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100Hz. The frequency of the sine wave is now around 40Hz. The frequency of the sine
wave can be further increased by decreasing the value of R1 and R2. If R1 and R2 are
changed to 16KOhms, the frequency will increase to 80Hz. The amplitude can also be
increased by changing the value of R6 to 1 KOhm. Remember to first disconnect the
output of the circuit from the BioRadio 150 before making any component changes to the
circuit.
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References
1. Thomas R.E. and Rosa A.J. The Analysis and Design of Linear Circuits. Prentice Hall,
Englewood Cliffs, New Jersey, 1994.
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