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EE 3010 - Laboratory
Experiment 7
Experiment 7: Introduction to LabVIEW and Digital Circuits
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Objectives:
 Become familiar with LabVIEW
 Simulate logic circuits using LabVIEW.
 Construct logic circuits using a standard breadboard, integrated circuits, and a light emitting
diode.
Week 1 Pre Lab:
 Bring a 3.5” diskette to lab. You will need it to save your files.
 Read and understand Section 9.4 in Hambley.
 Read and understand Sections 7.1 and 7.3 in Hambley.
 Examine the circuit of Part B. Create a truth table for this circuit.
Week 2 Pre Lab:
 Bring a 3.5” diskette to lab. You will need it to save your files.
 Read through Part D and complete steps 1 through 8 before coming to lab.
Part A: Become Familiar with LabVIEW
Work your way through the LabVIEW example starting on page 409 of Hambley. If you have
difficulties ask the lab instructor for help. When you have completed the virtual instrument
shown in Figures 9.24 and 9.25 have your lab instructor verify its operation.
Part B: Constructing Combinatorial Logic Systems with LabVIEW
1. Construct the logic circuit of Figure 1 using LabVIEW. Use Boolean toggle switches for the
A and B inputs. Connect X to a light-emitting diode (LED). Your front panel should look
like Figure 2 and the diagram should look like Figure 3. The switches and LED can be found
on the Boolean menu of the Controls Palette. The logic gates and inverter can be found on
the Boolean menu of the Functions Palette. Input A is high when the switch is up and low
when the switch is down. The LED lights when X is high.
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Experiment 7
Figure 2
Figure 3
2. Turn on the circuit by clicking on the run continuously button. Change switch states to test
all possible combinations of input logic states. Examine the output for each input state
combination and create a truth table to describe the results.
3. Does this truth table agree with the results from the Pre Lab and Step 4 Part B?
Part C: Constructing Combinatorial Logic Systems
1. Construct the digital circuit described by the digital schematic of Figure 1 using the
breadboard, integrated circuits (chips) provided. Verify the correct output of the
combinatorial circuit by using a light emitting diode. Follow the simple steps provided.
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Experiment 7
a. Examine the photograph of the breadboard below. Notice the array of holes in the
board. There are two thin strips of holes along the top and bottom edge of the
breadboard. These are connected electrically lengthwise along the edge of the board.
The voltage applied to any pinhole along the top row appears at every pinhole along
the row. Likewise, the next row inboard is electrically connected. The twin rows at
the bottom of the image are similarly connected. These strips are often used to
provide voltage that is common to all the components in the circuit, such as power, or
ground. You’ll notice that there is a connection from the top row to both of the chips
in this picture. Notice that they are from the same row on the top but where they are
placed in the column doesn’t matter.
b. Notice the twin strips of five rows each down the center of the image. These strips
are electrically connected VERTICALLY. Each column of holes is connected
together, but is insulated from the adjacent columns. This enables a single pin on one
of the chips to be connected to more that one wire. By placing the IC (chip) so that it
bridges the gap between the two strips, you can make connection to pins using 26gauge wire and construct your circuit. The holes on the breadboard are spaced so that
a standard integrated circuit will fit easily into the holes. A small amount of pressure
seats them into the holes and makes a good electrical contact.
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Experiment 7
Fig. 2
c. Notice that each chip has a small depression formed into its top surface near the lower
left corner of the case. This is an index mark. It tells you where Pin 1 is located.
You can see the diagrams that describe the connections, also known as “pin outs,” to
the chips you’ll be using below. These diagrams are extracted from a manufacturer’s
databook that describes the operation of the chips in more detail than is needed for
this exercise.
d. There are two input variables to the combinatorial circuit in Figure 1. They are A and
B. There are three Boolean functions required and each is implemented on a separate
CMOS (Complementary Metal Oxide Silicon) integrated circuit. The two input AND
gate is the MC14081CP , the two input OR gate is the MC14071CP and the
INVERTER is the MC14069.
e. Place the three chips on the breadboard the way you see them placed in the picture
above, so that they bridge the gap down the center of the breadboard, and with the
index mark in the lower left corner of the chip. One way to layout the chips is to
follow the logical flow of the circuit. Try putting the INVERTER on the left, the OR
gate in the middle and the AND gate on the right. Leave an inch or so between each
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Experiment 7
chip so things don’t get too crowded.
f. The next step is to apply the power supply voltage to the bread board. Using the
Power One regulated power supply, adjust the voltage output so it shows 5V. Double
check the voltage using the FLUKE45 Multimeter. Then connect V+ to the very top
and V- to the very bottom rows on the breadboard.
g. Each chip needs to be energized before it will function, connect a 5V power supply
wire from the top row of the bread board to pin 14(Vcc) of each chip and Ground to
pin 7 (Gnd) of each chip. If you put the index mark in the lower left corner, then pin
14 will be at the upper left corner, and pin 7 will be at the lower right corner.
h. Using the index mark as a reference, connect input A to pin 1 (A1) of the inverter.
The output of the inverter will be at pin 2 (Y1). Connect pin 2 (Y1) of the inverter to
pin 1 of the OR gate and input B to pin 2 of the OR gate. Remember that integrated
circuits look at voltage levels as inputs. Most logic circuit manufacturers guarantee
that their chip will acknowledge an input voltage of 4.3 V or higher as a logical ONE,
and any voltage below 0.3 V as a logical ZERO. For this exercise, you’ll set Vcc at
5V dc so you can connect a wire from the power supply or ground as your inputs A
and B. When you connect Vcc as an input, it will be recognized as a logic ONE.
When you connect ground to any input it will be a logic ZERO. As a general rule its
considered poor design to leave pins “floating.” Ambient noise or stray capacitance
can provide unintended inputs to the circuit and cause unanticipated outputs. Set the
unused AND gate inputs to a logic ONE and OR gate inputs to logic ZERO.
Pin assignment & logic diagram for the MC14069 Hex Inverter :
Fig. 3
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Experiment 7
Pin assignment & logic diagram for the MC14081CP Two Input AND gate
Fig. 4
Pin assignment & logic diagram for MC14071CP Two Input OR gate :
Fig. 5
The output of the OR gate will be its pin 3; connect that, and input A, (connect a "jumper" from
the input pin of the inverter where you first applied input A so that if your input changes it
automatically is applied everywhere simultaneously) to the two input AND gate. The output of
the AND gate will have to be connected to thr anode of the LED, it will illuminate when it is at
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the ‘1’ state and is off when the AND gate goes to the ‘0’ state. Notice that the LED has a long
lead and a short one. The long lead is the anode. Connect the cathode (short lead) to ground to
complete the circuit.
1. Ask your TA to verify your circuit before energizing it.
2. Create a truth table for this circuit that describes the behavior that you observe. Order the
rows of the truth table by counting up in binary to account for all combinations of input
states. Determine the output state for every possible combination of input states.
3. Does this truth table agree with that of the Pre Lab?
4. Examine the truth table outputs. Is there a simpler circuit that would perform the same
function?
Use Boolean algebra, truth tables, and Karnaugh maps to verify.
Part D: Digital Circuit Design
A Michigan Tech engineering student, Mr. I.M. Sharpe, has decided to automate his alarm clock
to eliminate the complex decision he must now make each morning at 6:30 AM—to get up or not
to get up.
Mr. Sharpe would like an automatic system to permit his alarm clock to ring or not based upon
certain conditions. A careful system analysis has resulted in the following decisions.
He will monitor four variables:
A. He will set a switch (A) the night before if he has an exam scheduled for 8 AM that morning.
B. An automatic snow monitor will set a switch (B) if there is a fresh snowfall of six inches or
more.
C. He will set a switch (C) if he was out late and partied too much the night before.
D. His friend next door who works in the dorm cafeteria will set a switch (D) any morning the
dorm is going to serve (ugh!) powdered eggs for breakfast.
The alarm should ring whenever he has an exam scheduled for 8 AM except when all three of the
other switches are set, i.e. except when it has snowed heavily, and he was out late, and there are
(ugh!) powdered eggs for breakfast. Under those conditions he will take his chances on a makeup
exam rather than get up. When no exam is scheduled for 8 AM, he wants the alarm silenced
when any two (or more) of the three switches (B, C, and D) are set. Otherwise, the alarm will
ring.
1. From the description above, create a truth table. (The inputs are 1 when the switches are set.
The output X is to be a 1 when the alarm rings.)
2. Write the direct Sum of Products expression for X (unreduced).
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3. Show that a reduced expression for X is
_ _ _ __ __ __
X=AC+AB+AD+BC+BD+CD
4. Draw the circuit diagram for X of step 3 using any of the following gates included with the
Ed-Lab:
5 Inverters, 4 AND (4 input), 3 NAND (4 input), 2 OR (4 input), 1 OR (3 input) and 3 NOR
(4 input).
Connect unused inputs of AND or NAND gates to logic '1' and unused inputs of OR or NOR
gate to logic '0' state.
5. An alternative is to design on the zeros of the truth table to generate X in Product of Sums
form. Write the direct product of sums expression for X (unreduced).
6. Show that an equivalent expression for X is:
_
_
_
X=ABC+ABD+ACD+BCD
7. You may use either Boolean Algebra or a Truth Table to verify this.
8. Draw the circuit diagram for X of step 3 using any of the following gates included with the
Ed-Lab:
5 Inverters, 4 AND (4 input), 3 NAND (4 input), 2 OR (4 input), 1 OR (3 input) and 3 NOR
(4 input).
Connect unused inputs of AND or NAND gates to logic '1' and unused inputs of OR or NOR
gate to logic '0' state.
9. Create a vi using LabVIEW to implement the expression of step 3. Use a LED for the alarm.
(I. M. Sharpe sleeps with his eyes open so he will see the LED if it lights.) Test the circuit for
all combinations of the input switches. Have your lab instructor check out the operation of
the vi.
10. Construct the circuit that you drew in Exercise 8 on the Edu-lab kit. The toggle switches are
set to 1 in the up position.
11. Have your lab instructor check out proper operation and initial the final circuit schematic.
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