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(closed notes, narrow vision, open mind) 4 test spring 2008
(The final exam is on ????? at ????? AM in this room.)
1. Draw the function diagram of an active low
logic device that will be active when a set of
alarm (limit) sensors present the equivalent
of 2638 to the inputs of that device.
2 A pnp transistor is saturated when its base is at 0 volts.
Yes __or No ___
3. Minimal current flows through a transistor when it is saturated.
Yes __or No ___
4. How many limit sensors are needed for the function diagram in question 1. _________
5. STOP buttons are normally closed active low devices.
Draw the wiring diagram for a STOP P.B. that will
interface to a TTL device. Label all voltage values.
6. Current flows in an LED when its anode is negative.
Yes __ or No ___
7. Current flows in a diode when its cathode is positive.
Yes __ or No ___
8. A diode is forward biased when its cathode is positive.
Yes __ or No ___
9. If a 20 ohm resistor is in series with a set of three
parallel 30 ohm resistors the total circuit resistance is
_________.
10 A 5 volt battery contains 1 coulomb of charged particles.
Yes __ or No ___
11 Stop push buttons are always active low normally open.
Yes __ or No ___
12.A pressure sense low device must be an active low device.
Yes __ or No ___
13. If a power supply with a Norton current of 3 amperes and Thevinin resistance
of 20 ohms is connected to a 40 ohm load, what is the circuit’s Norton resistance.
________
14. An pnp transistor is saturated when its base is at 0 volts.
Yes __or No ____
15. What is the current through
the load in question 13
______________
16. An pnp transistor is saturated when its base is at 0 volts.
Yes __or No ____
17. The emitter of a npn transistor is doped with a p-type atom.
Yes __or No ____
18. The emitter of a npn transistor is doped with a n-type atom.
Yes __or No ___
19. A TTL logic device is connected in series with a resistor and a LED. What
is the resistance value that limits the current in this circuit to 16 milliamps?
__________
20. A power supply with a Thevinin voltage of 120 volts and a 20 ohm Norton
resistance is connected to a 40 ohm load,
what is the Thevinin resistance value?
__________
21. What is the voltage drop across the
load described in the last question?
__________
22. What is the function diagram for an equivalent
Circuit of an NOR device?
23. What is the Department of Defense
Symbol for a two input NOR device?
24. When transistors are saturated the current through the collector is 0 amps. Yes __or No ___
25. Draw the Thevinin circuit described in question 20.
test 4 Instrument Systems
page 1 of 3
26. Item (12) is part of an asynchronous sequencer. Device U2 is a decoder
(1)
(2)
R
3
R2
R1
R2
V1
(3)
(a)
R3
R1
Yes____ or No____
(b)
(4)
(5)
Note
: DSP = device select
Control (step) number
pulse
Sequence
number
=x
=y
CX
DSP y-x
SY
(6) v
Out
RF
=-R
LED 1-3
Safety Alarm #1
FCE y-(x+1)
y alarm x
FCE y-(x+1)
DSP y-x
(7)
VIn
vOut =
- RF
I In
S3
S2
S1
S0
C3
C2
C1
C0
7
6
5
4
3
2
1
0
Expected status for the completion
of the current sequence step is
Enable stored in selected memory location
Wr/Rd
U6
(10)
(11)
R1
V
e
c
c Q
3
R2
(12)
LED2-3
1
2
A
3
A
U7
B
1
B
2
3
B
B
A=B
A
X
G
5 volts
C
A=B
A
Q
B
U1
Carry
5 volts
Q
Ck
X3
3
status from current
sequence step
2-1 LED
2-0
74161
5 volts
1Y0
C0
1Y1
C1
1Y2
C2
1Y3
C3
2Y0
S0
2Y1
S1
2Y2
S2
74139 2Y3
S3
U2a
1E
74139
2B
D
______________________
page 2 of 3
0
1
X2
2
1A
1B
2A
C
27. There are 4 possible 4 bit patterns that could be presented as the four
B inputs of the device labeled U7 in item (5).
28. Which icon on page 3 represents the TTL counter device? _______
29. Which item number above is the icon for a comparator operational
amplifier configuration?
30. Item (7) is a mathematical model for predicting the output voltage for
the circuit in item (9).
31. What day and what time is the final exam?
X
1
LED
Q
Q
From U7
X
0
Sequence
reset P.B.
Load
R3
test 4 Instrument Systems
A
0
2-2
CL
+
Q2
A
0
To Ck on U1
LED
+
LED1-0
FCE y-(x+1)
(9)
V
LED1-1
Safety Alarm #1
(8)
Q1
LED 1-2
2E
U2b
Yes____ or No____
__________
Yes____ or No_____
32. Device U6 in item (5) is a memory chip. The content of two memory locations in U6 are shown
below. If the binary pattern that corresponds to AD16 is on outputs D0, D1, D2, and D3, respectively,
then the A=B output on device U7 will go active when the binary pattern 1010 is
presented to X3, X2, X1, X0, respectively.
Yes___ or No____
Address of memory location
Content of memory location as base 16 value
ED16
AD16
EE
14
33 Examine the cartoon show to the right.;
(a) This is a diagram of a pnp transistor. yes___ no___
(b) The base material in this transistor is
positively charged.
yes ___ no ___
(c) Circle the circuit icon for this cartoon device.
(d) Label the parts of the correct circuit icon just above that represents the pnp transistor .
Use the circuit components below to help you answer the rest of the questions on this page.
(these questions are valued at 10 points each)
34. Draw a control scheme for a motor that when started will run for 9 hours and then stop automatically.
It has a Start push button, a Stop push button, and a LED that indicates the motor should be ON.
Note: The 555 device provides a steady stream of clock pulses at a rate of 1 clock pulse per hour.
16
3
4
5
6
9
2
+
V
A
Q
A
B
Q
74161
C
B
Q
D
C
Q
load
D
Power Supply
14
13
12
N.C.
11
motor
ck
15
carry
1
clear
7
Enable P
10
Enable T
PR 1
Gnd
Cl
1
ck
+ 10 V
C1
R1
PR 2
4
8
Cl
7
2
Out
Trigger
6
2
ck
Discharge
3
VOut
555
7474
Q
1
Q
1
Q
2
Q
2
- 10 V
35. Add a diode to your design above to provide current surge protection for the relay.
36. Add diodes to your design above to clamp the 555 output voltages to 5 V and/or 0V.
test 4 Instrument Systems
page 3 of 3