1. I.LI354
Programmable Logic Controller
Докторант .
Д. Пү рэвмагнай
1

2. Үйлдвэрлэлийн Технологи,
Дизайны Сургууль
Шинжлэх Ухаан Технологийн Их
Сургууль
Д. Пү рэвмагнай
Add. Монгол, Улаанбаатар, Багатойруу
Tel: +976-96638295
E-mail:
2
magnai@must.edu.mn, magnai320@yahoo.com

3. Сэдэв:
1. Удирдатгал
2. Түүх
3. PLCийн шинж чанар
4. PLC ийн ерөнхий фунцүүп
5. PLCийн ажиллах зарчим
6. PLCийн ангилал
7. PLCийн программчлал
8. Advantages and Disadvantages
9. PLCийн хэрэглээ PLCs’ Applications
10. PLCийн техник хангамж PLC hardwares
11. Жишээ
3

4. 4

5. Process Control & Automation
5

6. Технологийн процессын
автоматжуулалтын үе шат
PLC
CONTROL
ELECTRONIC
CONTROL
HARD WIRED
CONTROL
MANUAL
CONTROL
6

7. MANUAL CONTROL БУЮУ ГАР
УДИРДЛАГА
Энэ үед удирдлага болон тохируулгын бүхий л
үйл явц хүний үйлдлээр хийгддэг.
Гар удирдлагатай тохиолдолд хүнээс шалтгаалах
алдаанаас
хамааран
бүтээгдэхүүний
чанар
харилцан адилгүй байх ба бүтээгдэхүүний өртөг
өндөр байдаг
7

8. HARD WIRED БУЮУ РЕЛЕЙН ЛОГИК
УДИРЛАГА
8
Автоматжуулалтын хөгжилийн эхний
үед тоолууртай релей ашилагдаж
байсан.
Удирдлагын программыг өөрчлөх
тохилдолд
Програмп тохируулан релей
тоолууруудын холболтыг өөрчлөх
шаардлага үүсдэг байсан.
Энэ бүх үйлд ажиллагааг өнөө үеп PLC
хийх болсон

9. ELECTRONICS CONTROL БУЮУ
ЭЛЭКТРОН УДИРДЛАГА
Энэ үед удирдлагын хэлхээнд логик үйлдэлүүд
гүйцэтгэдэг элементүүдийг хэрэглэж эхэлсэн.
Хуучиг биметал мотоын таймер ашигладаг байсан
бол түүнийг электрон тоолуураар сольсон
Ингэснээр:
• Îðîí çàéã õýìíýñýí
• Ýíåðãè õýìíýñýí
• Çàñâàð ¿éë÷èëãýý áàãàññàí
9

10. PROGRAMMABLE LOGIC CONTROLLER БУЮУ
ПРОГРАММЧЛАГДАХ ЛОГИК УДИРДЛАГА
PLC
бол
микропроцессор
дээр
суурилсан
логик
зарчимаар
ажилладаг автомат удирдлага юм.
10

11. PLC-ийн тухай
Programmable logic controller (PLC) буюу
программчлагдах логик контроллер нь төрөл
бүрийн технологийн процессыг
автоматжуулахад ашиглагддаг дижитал
компьютер юм.
 Энэхүү автомат систем нь хуучин зуу эсвэл
мянган релей болон таймер ашигладаг
байсныг ганц PLC-ээр сольж программчилах
боломжийг бүрдүүлж байгаа юм.

11

12. Түүх :
•1960-аад оноос үүсэж жхжлсжн бөгөөд
•PLC нь 1970 оноос эхлэн үйлдвэрлэлийн удирдлагад
өргөнөөр ашиглаж эхэлсэн.
• PLC нь анх Америкийн машин үйлдвэрлэгчийн
(General motors) захиалгаар зохиогдсон.
•1980-аад оноос үнэ нь бууж эхэлсэн
• Одоо маш олон үйлдвэрлэлд өргөнөөр ашиглаж
байна.
12

13. Уламжлалт төхөөрөмжүүд
Devices
Релей Relays
Контактор Contactors
Мотор асаагуур Motor Starters
Гар үйлдэлт унтраалга Manually operated switches
Механик үйлдэлт унтраалга Mechanically operated
switches
Цахилгаан үйлдэлт унтраалга Electrically operated
switches
13

14. Релей Relays
Удирдлагын үндсэн элемент Original control
elements
Одоо бол туслах элементээр ашиглаж байна.
Now used as auxiliary devices
The PLC is not designed to switch high currents or voltages
CR1-1
CR1
14

15. Manually Operated Switches
Даралтат товчлуур Pushbuttons
Хэвийн нээлттэй Normally open
Хэвийн хаалттай Normally closed
Selector switches
Maintained or spring return
15

16. Механик үйлдэлтэй Унтраалга
Mechanically Operated Switches
Хязгаарын унтраалга
Limit Switches
Температурын унтраалга
Temperature Switches
Даралтын унтраалга Pressure Switches
Түвшиний унтраалга Level Switches
16

17. Цахилгаан үйлдэлтэй унтраалга
Electrically Operated Switches
Фотоэлектрик унтраалга Photoelectric Switches
Орон зайн унтраалга Proximity Switches
17

18. PLC-ийн шинж чанар
Characteristics of PLC
(1) Универсал байдал, уян хатан ба энгийн
монтажтай Versatility, flexibility and simple wiring
(2) Хүчтэй функцүүдтэй Strong function and expanpsion
(3) Өндөр найдвартай High reliability and strong antiinterference
(4) Программчлагддаг ба Programming and wiring can
synchronously
18

19. PLC-ийн шинж чанар
Characteristics of PLC
(1)Универсал байдал, уян хатан ба
цахилгааны энгийн монтажтай
PLC ийг удирдлагын системд төрөл бүрийн байдлаар
ашиглаж болдог. Тухайн PLC –г өөр төрлийн
удирдлагад ашиглахыг тулд техникийн өөрчлөл хийх
шаардлагагүй бөгөөд зөвхөн программчлалын хувьд
өөрчлөлт хийх шаардлагатай
"soft wiring"
19

20. PLC-ийн шинж чанар
Characteristics of PLC
(2) Хүчтэй функцүүдтэй Strong function
and expanpsion
Удирдлагын программчлал
Аналоги-Тоон болон Тоон-Аналоги
хувиргалт
Өгөгдөл дамжуулах процесс буюу сүлжээ
20

21. PLC-ийн шинж чанар
Characteristics of PLC
(3) Өндөр найдвартай High reliability and
strong anti-interference
Hardware:
Цахилгаан соронзон хамгаалалт, щүүлтүүр, оптик
холболт, хөндлөнгийн нөлөөлөлөөс хамгаалах.
Software:
Мэдээлэл хамгаалах, программчлалыг шалгах
систем
21

22. PLC-ийн үндсэн функц
Аналоги удирдлага
Логик удирдлага
PLC
Closed-loop удирдлага
22
Тооцоолуур
Network Сүлжээ

23. (1) Логик удирдлага.
Энэ бол хамгийн үндсэн функц.
Үүнд: ба, эсвэл, үгүйсгэх хэлбэр гэсэн функцүүд
ашигладаг ба унтраалга, релейн зарчимийг авч
явдаг
23

24. (2)Аналоги удирдлага
Үйлдвэрлэлийн процест маш олон төрлийн
хэмжигдэхүүнүүдийн өөрчлөлтүүдийг
ашигладаг жишээлбэл: температур, даралт,
хурд гэх мэт
Эдгээр хэмжигдэхүүнүүд нь бүгд аналоги
сигнал юм. RTD аналоги гаралт, оролтын
модулуудыг ашигладаг. Энд PLC ийг өргөн
ашигладаг.
24

25. (3) Closed-loop удирдлага
PLC зөвхөн запгай удирдлага хийхээс гадна
битүү хэлхээний удирдлага хийдэг.
Битүү хэлхээний удирдлага хийснээр PID хуулиар
удирдах боломжтой болж байгаа юм.
25

26. (4) Хугацаа, байрлал болон тоолуурын удирдлага
PLC ийн хугацааны удирдлагын функцүүдийг
ашигладаг эндээ импульсийн гаралтын
тохируулгууд хийж өгдөг
26

27. Network сүлжээ
(5) Network Communications
PLC ийг сүлжээнд холбосноор технологийн
процессийг хүссэн газраасаа хянах, удирдах
боломж бий болж байгаа юм.
27

28. 28

29. 29

30. PLC-ийн ажиллах зарчим
30

31. PLC-ийн ангилал
(1) Оролт гаралтын байдлаар
I/O points
(2)Бүтэцээр нь
By construction
31

32. PLC-ийн ангилал By I/O points
(1)Оролт гаралтын тоогоор
Оролт гаралтын портуудын тоогоор нь:
Micro: 32 I/O
Small: 256 I/O
Medium: 1024 I/O
Large: 4096 I/O
32

33. PLC-ийн ангилал
(2) Бүтцийн хувьд
By construction
 Compact PLCs
 Modular PLCs
33

34. PLC-ийн ангилал
(1) Compact
Monolithic construction
Monoprocessor
Fieldbus connection
Fixed casing
No process computer capabilities (no
MMC)
Fixed number of I/O (most of them binary)
(2) Modular PLC
Modular construction (backplane)
One- or multiprocessor system
Fieldbus and LAN connection
DIN-rail
Large variety of input/output boards
Connection to serial bus
34

35. Compact эсвэл modular ?
€
field bus
extension
compact PLC
(fixed number of I/Os)
modular PLC (variable number of I/Os
Limit of local I/O
# I/O modules
35

36. Programming languages
PLC программчлал
(1) Ladder logic диаграмм
(2) Statement list
(3) Функцийн блок диаграмм Function block
diagram
36

37. PLC программчлал
Ladder diagram
ladder diagram нь хамгийн
түгээмэл программчлалын хэл
The instructions are represented
:by graphic symbols
Contacts, Coils & Boxes
Statement list
37
Function block

38. Давуу тал
PLC нь бусад компьютерийг бодвол төрөл бүрийн
орчин ажиллах боломжтой оролт гаралт ихтэй
Siemens PLC
38

39. Давуу талууд:
 Flexibility:
 Correcting Errors:
 Space efficient:
 Low cost:
 Testing:
 Visual observation:
 Number of contacts many:
 Resistant character test :
 Simplifies the control system components
 Security :
 Documentation:
 Can make changes by reprogramming in seconds.
39

40. PLC-ийн хэрэглээ
40

41. PLC:Location in the control architecture
Engineer
station
Operator
station
Supervisor
Station
Enterprise Network
gateway
direct I/O
Field Stations
data concentrators,
not programmable,
but configurable
41
CPU
I/O
COM 2
Sensor Bus (e.g. ASI)
gateway
COM
FB
gateway
small PLC
PLC
Field Bus
COM
CPU
COM
I/O
I/O
I/O
COM
CPU
Field Bus
COM
CPU
I/O
I/O
I/O
I/O
directly connected
I/O
Control Station
with Field Bus
COM1
PLC
CPU
COM1
COM 2
I/O
I/O
I/O
I/O
large
PLCs
CPU
COM1
I/O
I/O
I/O
I/O
I/O
Control Bus
(e.g. Ethernet)
Field Devices

42. PLC-ийн бүрэлдэхүүн:
42

43. PLC-ийн үндсэн бүтэц
Power
CPU
Input
Devices
Input
module
Arithmetic
unit
Output
module
Control unit
Нэмэлт
Peripheral
I/O
Interfaces
43
MEMORY
EPROM
RAM
Өргөтгөл
Extension
I/O
Interfaces
Output
Devices

44. 44

45. 45

46. • CPU: дотоод төв процессороор микропроцессор
ашигладаг
• Power supply unit: Тэжээлийн эх үүсвэрийн
хувьд ерөнхий хувьсах A.C. хүчдэлийг тогтмол
бага хүчдэл D.C. болгон хувиргаж ашигладаг.
46

47. • Оролт гараотын хэсэг
Input-output sections:
Энд процессор гадаад
төхөөрөмжөөс мэдээлэл
хүлээн авах ба
холбогдсон гадаад
төхөөрөмжүүдэд
мэдээлэл дамжуулна.
47

48. • Нэмэлт модуль
Expansion Modules:
The S7-200 PLCs are expandable. Нэмэлт
модуль нь оролт гаралтын портуудыг
өргөтгөх зориулалттай.
Энэ модуль нь үндсэн төхөөрөмжтэйгээ
туузан холбогч /ribbon connector/ ашиглан
холбогддог.
48

49. • Санах ойн байгууламж
Memory unit:
төхөөрөмжийн
удирдлагад зориулагдсан
программыг хадгалахад
зориулагдсан.
49
• Программчлах
төхөөрөмж
Programming device:
энэ төхөөрөмжийг
ашиглан программыг
компьютороос санах ойд
бичнэ.

50. •PLCs invented to Replace
Relays and HARD WIRING:
Prior to PLCs, many of
these control tasks were
solved with contactor or
relay controls.
50

51. PLC системийг маш олон компаниуд гаргадаг:
Siemens,
Allen Bradley,
Omron,
Schneider,
гэх мэт
51

52. 52

53. S7-200 configuration
53

54. S7 200 family
54

55. S7-200 configuration
inputs
55

56. S7-200 configuration
outputs
56

57. S7-200 configuration
I/O numbering
57

58. Analogue I/O
Typical analogue signals from 0-10 VDC or 4-20 mA=
They are used to represent changing values such as
temperature, weight and level
58
speed,=

59. Instructions
:Standard instructions
.They are used in most programs
Examples: timer, counter, math, logical, incr., decr. and move
:Special instructions
They are used to manipulate data
.Shift, table, conversion, real time instruction
:High speed instructions
They allow for events and interrupts to occur independently of
.the PLC scan time
Examples: High speed counters and interrupts
59

60. Input Instructions
Bit Logic instruction
Normally Open contact
Normally Closed contact
Normally Open Immediate contact
Normally Closed Immediate contact
Positive Transition contact
Negative Transition contact
Not contact
60

61. Input contacts example
61

62. Output instructions
Output Instruction
Output Immediate instruction
No Operation instruction
Set (N bits) instruction
Reset (N bits) instruction
Set Immediate (N bits) instruction
Reset Immediate (N bits) instruction
62

63. Output, Set & Reset example
63

64. Starting a motor
64

65. Hard-wired DOL(direct-on-line ) starting
O.L. contact
Circuit Breaker
Contactor
Thermal
Overload
Star
t
Stop
Aux. contact
Contact coil
Induction
Motor
65
Induction Motor

66. Using PLC
Before start
Starting
After start
66

67. Stopping
67

68. Input & Output connections
68

69. Timer instructions
On-Delay Timer
Retentive On-Delay Timer
Off-Delay Timer
69

70. On-Delay & Retentive On-Delay timers
They count time when the enabling input (IN) is
ON. When the current value (Txxx) is > the preset
.time (PT), the timer bit is ON
The On-Delay timer current value is cleared when
(IN) is OFF, while the current value of the Retentive
.On-Delay Timer is maintained
You can use the Retentive On-Delay Timer to
.accumulate time for multiple periods of the input ON
70

71. Off-Delay timer
The Off-Delay Timer is used to delay turning an output OFF for a
.fixed period of time after the input turns OFF
When (IN) turns ON, the timer bit turns ON immediately, and the
. current value is set to 0
When (IN) turns OFF, the timer counts till PT and the timer bit
.turns OFF and the current value stops counting
If the input is OFF for a time shorter than PT, the timer bit
.remains ON
71

72. Timers numbers & resolutions
72

73. Timer examples
On-Delay
Retentive
On-Delay
Off-Delay
73

74. Hard-wired on-delay timer
74

75. le
75

76. TONR example
76

77. Timer example
77

78. Memory types
 You can access data in many CPU memory areas
- process image input register
- process image output register
- variable memory area
- Bit memory area
- sequence control relay memory area
- special memory bits
- local memory area
- Timer memory area
- counter memory area
- Analog inputs
78
(I)
(Q)
(V)
(M)
(S)
(SM)
(L)
(T)
(C)
(AI)

79. Memory addressing
)Accessing a Bit of Data in the CPU Memory (Byte.bit Addressing
79

80. Memory addressing
You can access data in many CPU memory areas (V, I, Q, M, S, L,
:and SM) as
.bytes, words, or double words by using the byte-address format
80

81. Memory types
 Process-image input register (I)
: Format
Bit
I[byte address].[bit address] I0.1
Byte, Word, Double Word I[size][starting byte address] IB4

Process-image output register (Q)
:Format
Bit
Byte, Word, Double Word

Q[byte address].[bit address] Q1.1
Q[size][starting byte address] QB5
Variable memory area (V)
:You can use V memory to
. store intermediate results of the control logic operations •
. store other data pertaining to your process or task •
:Format
Bit
Byte, Word, Double Word
81
V[byte address].[bit address] V10.2
V[size][starting byte address] VW100

82. Memory types
 Sequence control relay area (S)
They are used to organize machine operations or steps into equivalent
program segments. SCRs allow logical segmentation of the control
:Format
Bit
S[byte address].[bit address] S3.1
Byte, Word, Double Word S[size][starting byte address] SB4

Special memory bits (SM)
The SM bits provide a means for communicating information between the
CPU and your program. You can use these bits to select and control some
:of the special functions of the S7-200 CPU, such as
A bit that turns on for the first scan cycle•
Bits that toggle at fixed rates•
Bits that show the status of math or operational instructions •
:Format
Bit
SM[byte address].[bit address] SM0.1
Byte, Word, Double Word SM[size][starting byte address] SMB86
82

83. Memory types
 Local memory area (L)
The S7-200 PLCs provide 64 bytes of local (L) memory of which 60 can be
used as scratchpad memory or for passing formal parameters to subroutines.
Format:
Bit
L [byte address].[bit address] L0.0
Byte, Word, Double Word
L [size] [starting byte address] LB33
83

84. Memory types
Analog inputs (AI)
The S7-200 converts a real-world, analog value (such as temperature
or voltage) into a word-length (16-bit) digital value. You access these
values by the area identifier (AI), size of the data (W), and the starting
byte address. Since analog inputs are words and always start on
even-number bytes (such as 0, 2, or 4), you access them with evennumber byte addresses (such as AIW0, AIW2, or AIW4),as shown in
Figure Analog input values are read-only values.
Format: AIW [starting byte address] AIW4
84

85. Memory types
•Analog outputs (AQ)
The S7-200 converts a word-length (16-bit) digital value into a current
or voltage, proportional to the digital value (such as for a current or
voltage). You write these values by the area identifier (AQ), size of the
data (W), and the starting by address. Since analog outputs are words
and always start on even-number bytes (such as 0, 2, or 4), you write
), them with even-number byte addresses (AQW0, AQW2, AQW4
Format: AQW [starting byte address] AQW4
85

86. Replacing Relay by PLC
First step- We have to translate all of the items
we're using into symbols the plc understands
A contact symbol
A coil symbol
86

87. Second step
- We must tell the plc where everything is
located. In other words we have to give all
the devices an address.
Final step
- We have to convert the schematic into a
logical sequence of events.
87

88. Ladder Diagram and Programming:
Load: The load (LD) instruction is a normally open contact
A Load (contact) symbol
LoadBar: The LoadBar instruction is a normally closed contact.
A LoadBar (normally closed contact) symbol
88

89. Out :The Out instruction is sometimes also called an Output Energize instruction.
The output instruction is like a relay coil
An OUT (coil) symbol
OutBar: The outbar instruction is like a normally closed relay coil
An OUTBar (normally closed coil) symbol
89

90. Logic elements
90

91. Programming a PLC :
In order to create or change a program, the
following items are needed:
 PLC
 Programming Device
 Programming Software
 Connector Cable
91

92. You can use a personal computer as a programming device
92

93. Testing a program

Once a program has been written it needs to be tested and debugged. One
way this can be done is to simulate the field inputs with an input simulator.
 The program is first downloaded from
the PC to the CPU. The selector switch
is placed in the RUN position. The
simulator switches are operated and the
resulting indication is observed on the
output
93

94. Examples of Ladder
diagram(Example One):
We can simulate this same circuit with a ladder
diagram:
94

95. Examples of Ladder:
SIEMENS PLCs
• SIEMENS S7-200, CPU 222.
• 8 Inputs, 6 Outputs.
• 256 Counters & Timers.
95

96. Examples of Ladder diagram(Example two)::
Siemens PLC
96

97. Examples two
This Exam gives a complete understanding of input, output, OR and AND commands
in ladder diagram, and Timer. Here it is shown that if input I0.0 and I0.1 are on then
output Q0.0 will turn on and this part explains the AND command. Output Q0.0 can
also be activated if input I0.2 is on, which shows the OR command. In network two it
is shown that when input I0.3 is activated a timer will count 3 seconds
(300ms×10ms=3 s) and then this timer will activate the output Q0.1 .
97

98. Example three
In this assignment you are asked to imagine a parking lot. These are one entrance and
one exit in this parking garage. You are asked to draw the ladder diagram of this
system by considering the requirements mentioned here. Both the entrance and exit
gates are open with remote control and you can assume that there is a infrared sensor
to get the signal from the remote control and since this sensor is connected to PLC, as
it gets the signal it is processed in PLC and entrance or exit gate will open. There are
two infrared sensors one is placed toward the entrance and the other one is placed
toward the exit so they will not interfere. Since you need the system to keep the gate
open after someone presses the remote control button, you may need a latching switch
for both entrance and exit. In addition you need the gates to be open only for 20
second and the timing increment of your PLC is 10ms. Moreover since you do not
want the gate to damage your car if it takes more than 20 seconds to pass the gates,
there are 2 sensor placed at entrance and exit gate (one for entrance and one for exit)
to keep the gate open when a car is passing through.
98

99. Examples Continued
99

100. Example Solution
I0.0
Q0.1
SET
I0.1
T33
2000 10ms
100
M0.1
Q0.1
Reset
I0.0
T33
I02
Q0.1

101. Solution Description
In this example as I mentioned there should be a latching system to keep the
gate open and close it after a car passes through. Here I00 is the infrared
sensor that takes the command from the remote control. As it get the
command it opens the gate Q01 and at the same time it will activated the 20
second timer T33
I0.0
Q0.1
SET
101
I0.0
T33
2000 10ms

102. Solution Description Continued
After 20 second the timer activate the switch I01 which will reset the
output Q01, in other words it will close the gate. But this example does
not finish here. A sensor is required to keep the gate open if a car is
still in the gate way. So an other infrared sensor I02 is used here to
keep the gate open and it is connected to Q01.
I0.1
Q0.1
Reset
T33
102
M0.1
I0.2
Q0.1

103. Example four
Automatic water sprinkler system of a garden
This example is based on Automatic water
sprinkler system of a garden. It delivers water to
grass, flowers and trees. Watering of whole
garden depends upon humidity and temperature
conditions which are adjustable.
103

104. Example Picture
104

105. Example Continued
This example is one of the most complicated examples in this presentation. Here the
water sprinkler system (Q0.0) starts to work when either temperature sensor(I0.0) or
humidity sensor (I0.1) send a signal to it. In this scenario grass will be water first
(water the grass Q0.1) fro 4 second (it is assumed very small for simplicity) and then
flowers will be water (water the flowers Q0.2) for 10 second and at last trees will be
watered (water the trees Q0.3) for 18 seconds. Since it is required to avoid pressure
drop in the water line ,each section is separated and here the order to water this
garden is given: First grass, second flowers and third trees.
105

106. Example Continued
Here you can see that either temperature sensor I0.0 or humidity sensor I0.1 can turn
on the sprinkler system (Q0.0). If the humidity or temperature falls below a specific
point the system will start working.
106

107. Example Continued
107

108. Example Continued
In this Example it is needed to water the grass for 4 seconds. Since the increment is 10
ms, it is written 400ms in the timer. The input is assume to be the Q0.0 which was the
switch for sprinkler system. Here it is assumed that if the sprinkler is on, the output
Q0.1 will also become on and it will remain on for 4 seconds. If you take a look at the
ladder diagram you will see that the input Q0.0 turn the timer on and it will count 4
seconds until it breaks the second line.
108

109. 109

110. Example Continued
Since the input switch Q0.0 turn on all the timers in this ladder diagram at the same
time it is required to add the time for watering of each section with the time elapsed
in the previous sequence. For example although it is required to water the flowers
for only 10 second but in the timer it is written 1400ms with the increment 10 ms
which will eventually be equal to 14 second. Now if you subtract 14 seconds from 4
second (the time required for the first section) you will get the required time which
is 10 seconds. There is one more important parameter here. In the ladder diagram it
is written if the first section is done start the second section. You can see this in the
second line of the ladder diagram. The output here is Q0.2 which is assumed for
watering flowers.
110

111. Example Continued
111

112. Example Continued
This part is like the second part. Watering the trees is started when previous section
are finished. The time for this section is 18 second which is added to 14 seconds
counted before and now it is written as 3200 ms with 10ms increment. You can see
when both Q0.1 and Q0.2 are off the third part (Q0.3) is started.
112

113. Example five
This example is based on a parking lot with a PLC which counts the
number of cars that enter and exit and if the parking lot is about to be full,
PLC sends a signal to a electronic board to say that the parking is full. The
system is also utilizing a infrared sensor to open the gates with remote
control.(The capacity of this parking lot is assumed to be 5 cars.)
113

114. Solution
114

115. Example Continued
In this example input I0.0 open the entrance gate and input I0.1 opens the exit
gate. I0.0 and I0.1 are both infrared sensors which will be activated by remote
control. In addition sensor I0.2 count the number of cars entering the parking lot
and sensor I0.3 counts the cars leaving . The switch I0.4 is used to reset the
system. If a total number of 5 cars enter this parking lot, counter C1 send a signal
to the electronic board Q0.2 to show that the parking is full.
115

116. Programmable logic control
 A PLC has many "input" terminals, through which it interprets
"high" and "low" logical states from sensors and switches.
 It also has many output terminals, through which it outputs "high"
and "low" signals to power lights, solenoids, contactors, small
motors, and other devices lending themselves to on/off control.
 In an effort to make PLCs easy to program, their programming
language was designed to resemble ladder logic diagrams.
 Thus, an industrial electrician or electrical engineer accustomed
to reading ladder logic schematics would feel comfortable
programming a PLC to perform the same control functions.
116

117. Program design of PLC
Design objective
PLC selection and resource allocation
I/O address assignment
Wiring
Programming
117

118. Layout of Intersection Trafic Lights
North
G
Y
R
G Y R
West
R
Y
G
R Y G
South
118
East

119. I/O address assignment
Serial number
1
I0.0
Start swich
2
I0.1
Stop
3
I0.2
emergency stop button
4
Q0.0
North-South Green
5
Q0.1
North-South Yellow
6
Q0.2
North-South Red
7
Q0.3
East-west Green
8
Q0.4
East-west Yellow
9
119
address
Notes
Q0.5
East-west Red

120. AC220
N
L
Q0.0
I0.0
I0.1
Q0.1
I0.2
Q0.2
24V(L+)
Hardware Wiring
PLC
CPU224 Q0.3
AC/DC/ RLY
Q0.4
1M
Q0.5
M
1L
2L
120
AC220
AC220