Question Bank Programmable Logic Controller

Programmable Logic Controller
Question Bank
Department of Electronics Engineering
Dr. Nilesh Bhaskarrao Bahadure

Page 1

QUESTION BANK
Sub: Programmable Logic Controller (M.Tech)

UNIT – I
01. What is programmable logic controller, explain block diagram of programmable
logic controller.
02. Explain in details the components used in the programmable logic controller.
03. Draw and explain the programmable logic controller program scan.
04. Write short notes on fixed input/output and modular input/output.
05. Explain symbols used in the programmable logic controller.
06. Explain in details the ladder diagram rule with suitable example.
07. Draw and explain input and output adjustable interface of the PLC.
08. Give comparison between computer control system and PLC control system.
09. Draw 3 inputs AND, OR and NAND gate PLC ladder diagram.
10. Draw and explain 3 inputs NOR, NAND and EXOR gate PLC ladder diagram.
11. Solve the following.
(a) Output 100 is to be ON only when either input 7 and 8 are ON or if input 17 and
input 18 are ON. Output 100 can be ON when all the four inputs are ON. Draw
ladder relay and PLC logic
(b) Conveyer C is to run when any one of four inputs are ON, it is stop when any one
of four other inputs is ON. Draw ladder relay and PLC logic. Use Push button
switches.
(c) For output 7 to be on, input 6 must be off and either input 8 or input 9 must be
on. In addition one of inputs 1, 2, or 3 must be on.
(d) For output H to be on, input A must be on and both inputs C and D must be off. In
addition one or more of inputs E, F and G must be off.
12. Solve the following
Total Questions 99

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(a) Design a motor control circuit with two start and two stop buttons. When a start
button is depressed, the motor runs. By sealing, it continuous to run when the
start button is released. Either stop button stops the motor when depressed.
(b) Switch 8 and switch 11, plus either switch 22 or switch 34, must be on for
output 76 to be on.
(c) Design relay logic and PLC logic. A process fan is to run only when all of the
following conditions are met.
(i) Input 1 is OFF
(ii) Input 2 is ON or input 3 is ON
(iii) Input 5 and 6 are ON
(iv) One or more of the inputs 7, 8 and 9 is ON
13. Convert a given PLC ladder diagram to the equivalent gate diagram.
(a)

Figure (1)
(b)

Figure (2)

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(c)

Figure (3)

14. Convert a given gate diagram into ladder diagram.
(a)

(b)

(c)

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(d)

(e)

UNIT ‐ II
15. Explain the types of the registers of the programmable logic controller.
16. What is holding register, explain holding register in details.
17. Explain input and output registers of the PLC.
18. Draw and explain input group register of the PLC with suitable example.
19. Draw and explain output group register of the PLC with suitable example.
20. What is module addressing, explain module addressing used in the PLC.
21. Explain single and group input register in details.
22. Explain single and group output register in details with suitable example.
23. Show the contents of the input and output register by observing given ladder
diagram.

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24. Show the contents of the input and output register by observing given ladder
diagram.

25. Explain the following instructions of the PLC.
(a) XIO
(b) OUTB
(c) SET
(d) OTU
(e) AND
26. Explain the block format of the following instructions. Explain with suitable
example.
(a) ADD
(b) SUB
(c) MUL
(d) DIV
(e) SQR
(f) SIN
(g) TAN
(h) ACS
(i) LN
(j) LOG
(k) XPY
(l) NEG
27. Draw and explain block format of all timers instruction. Explain with suitable
example.
28. Draw and explain block format of all counters instruction. Explain with suitable
example.
29. Design an application to run a motor, when counter counts 100 pulses. Use IN 0001
as an input sensor for the count and IN 0002 as an enable / reset function. Design
using count up and count down.
30. Design an application that an output indicator to go ON when 6 of part C and 8 of
part D are on a conveyor. Use IN 0002 and IN 0003 as a proximity devices that pulse
ON for part C and part D. in order to repeat the process use master control relay
using IN 0001.

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31. Design an application to keep a track of net number of parts on a conveyor. The
number of parts going on a conveyor is counted by one proximity devices count.
The number leaving the conveyor is counted by 2nd proximity devices count.
32. Design an application, when count 100 is reached, a paint spray is to run for 50
second. Use IN 0007 for the count, IN 0008 for Enable / Reset.
33. Design an application to run a motor. A motor runs after counter counts 100 pulses.
A counter counts 100 pulses only after 1 hour of the process starts.
34. An indicating light is to go on when a count reaches 23. The light is then go off when
count reaches 31.
35. A machine M is to be turned ON either when count A goes up to 11 or when count B
goes up to 16. One stop button or switch resets the entire process.
36. Write short notes on comparison instruction of the PLC.
37. Explain basic comparison instructions of the PLC.
38. Design a system that compares the received values from input register IR 0005
with constant number 0087. If the values are not equal then output is ON and if the
value becomes equal then output is OFF. Design using Equal and Not Equal
functions.
39. Design a system to compare two count values in order to run a production system.
If the count is greater than 348 then system is ON. Design using
(a) Greater than function, assume greater than function directly available.
(b) Derived greater than using greater than or equal to function and equal to
function.
40. Explain following comparison instructions with suitable examples.
(a) EQU
(b) NEQ
(c) GEQ
(d) LES
(e) GRT
(f) LEQ

UNIT ‐ III

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41. Explain the different numbering system used in the PLC.
42. Write short notes on decimal and binary number system with suitable example.
43. Write short notes on BCD number system; give comparison between decimal and
BCD number system.
44. Write short notes on octal and hexadecimal number system.
45. Explain binary and gray code numbering system. Explain the differences between
this two.
46. Convert following binary numbers to decimal, octal and hexadecimal.
(a) 111
(b) 1011
(c) 1110101
(d) 1101101
(e) 10110011
(f) 100110111110
47. Convert following decimal numbers to binary, octal and hexadecimal.
(a) 14
(b) 42
(c) 85
(d) 162
(e) 207
(f) 459
48. Convert following decimal numbers to BCD.
(a) 56
(b) 381
(c) 1121
(d) 5476
(e) 6666
(f) 4562
(g) 7745
49. Convert following BCD numbers to decimal
(a) 0110 0011 1011 1100
(b) 0110 0011 0111 0110
(c) 1000 1001 0100 0001
(d) 0101 0000 1000 0101
(e) 0011 0011 0011 0111
(f) 1001 1000 0011 1000
(g) 1000 0101 0100 0111
50. Convert following decimal numbers to the base 3 and base 4
(a) 23
(b) 12
(c) 45
(d) 34
(e) 44
(f) 21
51. Convert following hexadecimal numbers to binary, octal and decimal.
a) 11
b) 3C
c) 2A2
d) BCF
e) 1B4C
f) DDDDD

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g) A0C4 h) FF34 i) 34DC
52. Explain SK and MCR instructions of the PLC using suitable example. Clearly
indicates the differences between this two.
53. Explain JMP and LBL instructions of the PLC with suitable example.
54. Explain jump with non return and jump with return instructions of the PLC with
suitable examples.
55. Explain single and block transfer instructions of the PLC, explain with suitable
example.
56. Explain MOV and BT instructions of the PLC, explain with suitable example.
57. Explain BS, BC and BF instructions of the PLC, explains with suitable example.
58. Design an application to perform addition of 0015, 0016 and 0017 using
subroutine. Perform addition after timer elapses 25 seconds.
59. Design a system to perform subroutine of multiplication of two numbers 1234 and
5678, perform multiplication after counter counts 100 pulses.
60. Design an application to transfer block of 10 bytes from the starting source register
HR 0050 to starting destination register HR 0100. Also write subroutine to add the
contents of the entire destination registers and put the result in holding register
HR 0200. Ignore the carry flag if generated.
61. Design an application to transfer 5 double word from last source register HR 0050
through last destination register HR 0100. Write a subroutine to perform addition
of first half of the destination registers contents and then again call a subroutine to
perform subtraction of the remaining numbers from the added value. Put the result
in the destination register HR 0200.
62. Assume that holding register HR 0070 consist 0000 values, show the contents of
data in function so that the value of HR 0070 becomes 9ABC.
63. Assume that holding register HR 0070 consist 0000 values, show the contents of
data in function so that the value of HR 0070 becomes 8765.
64. Explain block format of BSR and MSR instructions of the PLC, explain with suitable
example.

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65. Explain block format of BSL and MSL instructions of the PLC, explain with suitable
example.
66. Show the contents of the holding register HR 0070, HR 0071 and HR 0072 after
executing following block.

Assume initial contents of the HR 0070 = 9ABC, HR 0071 = 3456 and HR 0072 =
C459. Show the contents for the data in = 0 and data in = 1.


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70. Explain the sequencer used in the PLC, explain with suitable example.
71. Explain the block diagram instruction of sequencer output (SQO), with suitable
example.
72. Place the machine matrix shown in the figure given below in a PLC sequencer
program. Program for manual, event actuated operation.
Step Number Machine Number
7 6 5 4 3 2 1

1 ‐ ON ‐ ‐ ‐ ‐ ‐
2 ‐ ‐ ON ON ‐ ‐ ‐

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3 ON ‐ ‐ ‐ ON ON ON
4 ON ON ON ON ON ON ON
5 ‐ ‐ ‐ ‐ ‐ ‐ ‐
6 ON ‐ ON ‐ ON ‐ ON
7 ‐ ON ‐ ON ‐ ON ‐
8 ‐ ‐ ON ‐ ‐ ‐ ON
73. Explain how to reduce program length and to reduce complications in the program
using PLC matrix functions.
74. List the advantages of PLC matrix function over other calculations, justify your
answer by suitable example.
75. Differentiate between the operation by basic mathematical matrix function and
PLC matrix function.
76. Explain PLC AND and PLC OR matrix function with their instruction sets.
77. Explain how to derived PLC NAND and PLC NOR matrix function using PLC AND and
PLC OR function with PLC Complement function. Justify your solution by
considering two data’s 1234 and 9ACB.
78. Explain PLC Complement and PLC Compare matrix function with suitable example.
79. Create two matrices of your own design with 43 active bits. In a 16 bit PLC, matrix
analysis will require two full register plus part of the third. Find the solution to
functions of your choice manually and by the PLC. Compare the result for exact
correspondence.

80. Solve the following using Matrix A and Matrix B
Matrix A Matrix B
1 0 0 1 1 1 1 0 0 1 1 0 1 0 0 1
0 0 1 1 0 0 0 1 1 1 1 1 1 1 1 1
1 1 1 0 0 1 1 1 1 0 1 0 1 0 1 1
0 1 0 1 0 0 0 1 0 0 1 1 1 1 0 0

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1 1 0 1 1 1 0 0 1 0 1 0 1 0 1 1
0 0 0 1 0 0 1 0 1 1 0 1 0 0 1 0
0 0 0 0 0 0 0 1 1 0 1 1 0 0 0 1
1 0 1 0 1 0 1 0 0 1 0 0 0 1 1 1

a) AND A and B to determine matrix C
b) OR A and B to determine matrix D
c) XOR A and B to determine matrix F
d) Compare A and B to determine matrix F.
e) Complement matrices A, C and E to determine matrices G, H and I.
f) NAND B and C to determine matrix R.
g) NOR A and C to determine matrix S.

UNIT – IV & V
81. Write short note on analog PLC operation.
82. Explain analog BCD input and output system with suitable example.
83. What is PID controller system? Explain PID control system in details.
84. How does proportional – integral process control system improve control
compared to proportional control only?
85. How does proportional – integral – derivative process control system improve
control compared to proportional – integral control only?
86. Draw and explain block diagram of typical PID controller.
87. What is networking PLC’s, explain in details.
88. Explain the differences between discrete type PLC and analog type PLC.
89. Draw and explain distribution of processing tasks in a plant according to the
function.
90. Draw and explain open system interconnection system used for the networking
and communication.

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91. Explain in details the network communication associated with PLC.
92. Differentiate between WAN and LAN.
93. Explain different languages used for the PLC programming. Explain by assuming
suitable example.
94. Differentiate between block diagram language and Boolean mnemonics language.
95. Explain the factors responsible for the reliable operation of the PLC after
installation.
96. Explain the differentiation between the PLC and PC in various aspects.
97. Explain the important features of the programmable logic controller and also list
the different languages used for the PLC programming.
98. Explain what are the factors to be considered for selecting the suitable
programmable logic controller.
99. Write short notes on maintenance and troubleshooting of the programmable logic
controller.

Question Bank Programmable Logic Controller

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Question Bank Programmable Logic Controller