Practice Problem
You have just completed the design of a simple AND logic circuit that will
activate a motor. This motor requires a high signal to start the motor.
(The motor input is an active high input.)
Test your circuit design at the bread board
level.
First, let’s review the structure and use of a breadboard.
The Breadboard
What You Don’t
See See:
The Breadboard
What You Don’t See:
Horizontal strip of
copper wire.
Horizontal strip of
copper wire.
Horizontal strip of
copper wire.
Two rows of short isolated
vertical strips (70 single strips
per row) of copper wire
Horizontal strip of
copper wire.
The Breadboard
Power Supply
+
+ 5 volts
Ground ( 0 V )
0 volts
Power and ground rails
25 nodes per
horizontal row
section
5 nodes per
vertical column
5 volt horizontal
panel
The Breadboard
Power Supply
+
+ 5 volts
0 volts
Power and ground rails
25 nodes per
horizontal row
section
5 nodes per
veridical column
A node is a point where two components of a circuit can be connected.
The Breadboard
Vertical Column (5 Node) :
Each Vertical Column on the face of the board has a strip of metal
underneath the board connecting the 5 holes. This allows 5 different
circuit elements to be connected and have the same voltage value.
+5 volt node
connection
Ground, 0 V,
node connection
Each column of the breadboard is electrically isolated from its neighbor
The Breadboard
The Trench
(A nonconductive groove
which isolates 2 groups of
vertical columns)
The “chip”
Chips are to be installed across the Trench
In this case, the chip is called a 7408 and it houses four AND logic devices.
The Breadboard
The chip with the identification number 7408 is always a chip that
contains AND devices. How many AND devices are in a 7408 chip?
Input # 1 for
AND device C
The Breadboard
Output for AND
device B
Pin 14
Input # 1 for
AND device A
Input # 2 for
AND device C
Input # 1 for AND device D
Input # 2 for device D
A
Output for
device D
Pin 1
C
B
D
Input # 2 for
AND device A
Pin 7
Output for AND
device A
Input # 1 for
AND device B
Input # 2 for
AND device B
Pin 8
Output for AND
device B
There are 4 AND devices in the
7408 package.
The 7408 is know as a quad 2 input AND package.
The Breadboard
In order to perform its function each chip must have a
connection to the Power (5V) and to the Ground (0V)
What are the possible pins that could be used for the power and ground connection?
Input # 1 AND device A
Input # 2 AND device A
Input # 1 AND device C
Output AND device A
Input # 1 AND device C
Input # 1 AND device A
Output AND device C
Input # 2 AND device A
Input # 1 AND device D
Output AND device A
Input # 1 AND device D
Output AND device D
There are two pins left. One is for the power connection, the other is for the
ground connection.
Which one goes to which pin?
The Breadboard
In order to perform its function each chip must have a
connection to the Power (5V) and to the Ground (0V)
What are the possible pins that could be used for the power and ground connection?
14
Input # 1 AND device A
+
The terminal where the 5
volt wire is connected.
Input # 2 AND device A
Input # 1 AND device C
Output AND device A
Input # 1 AND device C
Input # 1 AND device A
Output AND device C
Input # 2 AND device A
Input # 1 AND device D
Output AND device A
Input # 1 AND device D
The terminal where the
zero volt wire is
connected, (the ground
connection).
-
7
Output AND device D
The Breadboard
Where
How many
are the
pins
power
does and
a 7408
ground
have?
connections for this 7408?
14
Which one is the pin where the 0
volts, the ground connection, is
made?
Power (+5 ?Volts)
Which pin is pin number 8?
Which pin is pin
number 14?
Note:
Which pin is pin
number 7?
If you hold the
chip so you can
read the label
“DM 7408N”,
14
Then the 5 volt
pin is the last
pin on the left
side of the top
row of pins.
7
Which pin is pin number 1?
?
Ground ( 0 Volts)
The Breadboard
Practice Problem
Now let’s return
to the initial
problem
statement
You have just completed the design of a simple AND logic circuit
that will activate a motor. This motor requires a high signal to
start the motor. (The motor input is an active high input.)
Test your circuit design at the bread board level.
When
the circuit
two inputs
(input
A andbefore
inputyou
B) continue
are at logic
thepresentation.
Draw
your test
on a piece
of paper
with1this
output will be at logic 1 and the meter will display 5 volts.
Power (+5 Volts)
A ( input ) 1
Battery powered
Volt meter
1
1
4.96
0
+
B ( input)
0 Volts
The Breadboard
Practice Problem
Now let’s return
to the initial
problem
statement
You have just completed the design of a simple AND logic circuit
that will activate a motor. This motor requires a high signal to
start the motor. (The motor input is an active high input.)
Test your circuit design at the bread board level.
When
the circuit
two inputs
(input
A andbefore
inputyou
B) continue
are at logic
thepresentation.
Draw
your test
on a piece
of paper
with1this
output will be at logic 1 and the meter will display 5 volts.
Power (+5 Volts)
A ( input ) 1
Battery powered
Volt meter
1
1
4.96
0
+
B ( input)
0 Volts