1. CHAPTER 3 INTRODUCTION TO PROGRAMMABLE LOGIC CONTROLLER
BY: Salsabila Ahmad

2. INTRODUCTION TO PLC History of PLC Advantages of PLC PLC Operations
Serial and Parallel Circuit
Serial Circuit
Parallel Circuit
Numbering System
Boolean Algebra
Ladder Logic Diagram
Q&A

3. HISTORY OF PLC
In the early days; all stages in a process were done by hand
As depicted in figure
the filling
capped
labeling
packing processes
are done totally manually

4. After the industrial revolution
entire processes were automated
filling, labeling and packing are all being done by machines controlled electro-mechanically

5. Then invention of computers brought
a new method of automation control, the Programmable Controller.
That time, a more efficient PC is managing the bottling process
Substituting the old relay control system.

6. As technology expands further, today
the same bottling processes
use a central control system
linking many PCs together

7. ADVANTAGES OF PLC Flexibility Large quantities of contact Lower cost
Ease of pilot running
Visual observation
Speed of operation
Reliability
Security
Ease of documentation
Ease of changes by reprogramming

8. PLC OPERATIONS
CHECK INPUT STATUS
EXECUTE PROGRAM
UPDATE OUTPUT STATUS

9. PLC can continuously perform the cyclical task of scanning, a process which involves
reading the inputs,
executing the user program
updating the outputs
without requiring a user program to direct it to do so.

10. A PLC is designed to perform logic functions previously done by
electromechanical relays,
mechanical timers/counters
to control the manufacturing process.

11. The operator enters a sequence of instructions
program into the PLC memory.
The controller then monitors the inputs and outputs according to the program
The controller carries out the control rules

12. Step 1 CHECK INPUT STATUS
First the PLC takes a look at each input to determine if it is on or off. In other words, is the sensor connected to the first input on? How about the second input? How about the third... It records this data into its memory to be used during the next step.

13. Step 2
EXECUTE PROGRAM
Next the PLC executes your program one instruction at a time. Maybe your program said that if the first input was on then it should turn on the first output. Since it already knows which inputs are on/off from the previous step it will be able to decide whether the first output should be turned on based on the state of the first input. It will store the execution results for use later during the next step.

14. Step 3
UPDATE OUTPUT STATUS-Finally the PLC updates the status of the outputs. It updates the outputs based on which inputs were on during the first step and the results of executing your program during the second step. Based on the example in step 2 it would now turn on the first output because the first input was on and your program said to turn on the first output when this condition is true.
After the third step the PLC goes back to step one and repeats the steps continuously. One scan time is defined as the time it takes to execute the 3 steps listed above.

15. HOW TO APPLY HERE?

16. Conventional series circuit
SERIAL CIRCUIT
Can also be referred as
AND logic function
where all switch must be closed (ON)
for output to energized (ON)
SW1
SW2
Battery
LMP1
Conventional series circuit

17. Series circuit represented in conventional ladder rung
Or it can be represented
In schematic ladder diagram
As:
LMP1
SW1
SW2 L1 L2
Series circuit represented in conventional ladder rung

18. LADDER DIAGRAM To energized LMP1 SW1 and SW2 need to be closed05
PLC representation of previous rung using Allen- Bradley MicroLogix1000

19. Program listing / Mnemonic Code
LOAD I1
AND I2
OUT 05
for Allen-Bradley
MicroLogix1000
Note:
The instructions tell the processor to
load input (I1) into memory,
AND it with input2 (I2),
then output the result to output5 (O5)
Notice the operands for input differ
OMRON use 00001
Allen Bradley use I1 (for input 1)
While operands for output
OMRON use 01000
Allen Bradley use O1 (for output 1)

20. AND TRUTH TABLE ? A B C 1

21. Can we have more than 2 inputs for AND logic? Yes
We can have more than 2 inputs for AND logic but the outcome will still be the same
when all inputs ‘ON’.
output will only be energized ‘ON’
SW1
SW2
SW3
LMP1 I1 I2 I3 01
Three- input PLC ladder rung

22. PARALLEL CIRCUIT Can also be referred as OR logic function
where at least one switch must be closed (ON)
for output to energized (ON)
SW1
SW2
LMP1
Battery
Conventional parallel circuit

23. Or Or it can be represented In schematic ladder diagram As:
LMP1
SW1 L1 L2
SW2
Parallel circuit represented in conventional ladder rung

24. LADDER DIAGRAM ? To energized LMP1 SW1 OR SW2 need to be closed02 ?
SW2 I2
PLC representation previous rung using Allen- Bradley MicroLogix1000

25. OR TRUTH TABLE ? A B C 1

26. CONSIDER…. What is the Mnemonics Code for OMRON CPM1A? LD 00001
LMP1
SW1 02 I1
SW2 I2
SW3 I3
Three- input OR logic
What is the Mnemonics Code for OMRON CPM1A? LD OR OR
OUT

27. NUMBERING SYSTEMS In our daily, we use the decimal numbering system
But, besides decimal, knowledge of
Binary
16 bit group binary number
Binary Coded Decimal
octal
hexadecimal
numbering system is essential when using the PLCs
EXAMPLE 1
EXAMPLE 2
Comparison of the Number Systems

28. DECIMAL SYSTEMS Decimal System Uses in daily life
Uses only ten digits ;
0, 1, 2, 3, 4, 5, 6, 7, 8 and 9
The first column can hold up to 9
the second column can hold up to 90(nine 10s),
the third column represents the number of hundreds
and so forth and so on.
Decimal System
100,000s
10,000s
1000s
100s
10s 1s

29. For example, 328 represents three 100s two 10s and eight 1s
Decimal number
8 x 100 =
2 x 101 = 20
3 x 102 = 300
Decimal number
32810

30. BINARY SYSTEMS Binary System 1 1 0 0 1 1 0 1 2
Used by computers and PLCs
Use only two digits;
0 and 1
Base 2
Works similarly to decimal systems
Binary System
32s
16s 8s 4s 2s 1s
Binary number
1 x 20 = 1
0 x 21 = 0
1 x 22 = 4
1 x 23 = 8
0 x 24 = 0
0 x 25 = 0
1 x 26 = 64
1 x 27 = 128
Decimal number
20510

31. 16-BIT GROUP BINARY NUMBER
Most Significant Byte
Least Significant Byte
Nibble
Word
1 nibble= 4 bits
1 byte= 8 bits
Size of word depends on the processor;
16-bit processor has 16-bit word while a
32-bit processor has a 32-bit word

32. BINARY CODED DECIMAL
In BCD, 4 binary bits are used to represent a decimal digit.
These 4 bits are used to represent the number 0 through 9.
Note: BCD is not the same as binary!
The decimal number of 205 is
In BCD
but in Binary
(refer binary note)

33. OCTAL SYSTEM Octal System Use only 8 digits; 0,1,2,3,4,5,6 and 7
Base 8
Octal System
32,768s
4,096s
512s
64s 8s 1s
Octal number
7 x 80 =
0 x 81 =
2 x 82 = 128
3 x 83 = 1536
Decimal number
167110

34. HEXADECIMAL SYSTEM Used 16 digits but with an unusual twist1 2 3 4 5 6 7 8 9 A 10 B 11 C 12 D 13 E 14 F 15
Used 16 digits
but with an unusual twist

35. HEXA DECIMAL 2 0 D 16 Hex number D x 10 = 13 0 x 161 = 0
Decimal number
52510

36. HEXA  BCD  HEXA
Each hex digit is simply converted to its four-digit binary (BCD) equivalent and vice versa
7 D F
hexadecimal
binary
hexadecimal
7 D F

37. EXAMPLE 1 16 Bit Binary 1001 0010 1011 0101 Grouped Binary Hexadecimal
Equivalent
9x x x x160
36, 864
512
+ 176 5
37,55710 B
DECIMAL?

38. EXAMPLE 2
Most Significant Number (MSD)
Least Significant Number (LSD)
Middle Digit, MD
BCD number
=23910
DECIMAL?

39. COMPARISON BETWEEN THESE NUMBER SYSTEMS

40. Decimal Hexadecimal Octal Binary 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 11 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 A B C D E F 8s 1s 1 2 3 4 5 6 7 8s 4s 2s 1s 1

41. BOOLEAN ALGEBRA Mathematical system of logic Used only
two digits (0,1)
2 states (true, false)
are used in logic problem
Types of functions OR
AND
NOT
NOR
NAND
XOR

42. OR relationship A and B wired in parallel Boolean equation; A + B = C
OR Truth table C A B
OR gate A B C 1
OR Truth table

43. AND relationship A and B are wired in series.
Boolean equation; A . B = C
AND Truth table C A B
AND gate A B C 1
AND Truth table

44. NOT relationship Boolean equation; Ā = B NOT Truth table A B Ā B 1
NOT gate
Boolean equation; Ā = B
NOT Truth table Ā B 1
NOT Truth table

45. NAND function AND of NOT Boolean equation; Ā + B = C NAND Truth table
NAND gate
AND of NOT
Boolean equation; Ā + B = C
NAND Truth table A B C 1
NAND Truth table

46. NOR function OR of NOT Boolean equation; Ā . B = C NOR Truth table A B
NOR gate
OR of NOT
Boolean equation; Ā . B = C
NOR Truth table A B C 1
NOR truth table

47. XOR function Boolean equation; A.B + Ā.B = C XOR Truth table A B C 1 C
XOR gate
Boolean equation; A.B + Ā.B = C
XOR Truth table A B C 1
XOR truth table

48. LADDER LOGIC DIAGRAM Introduction Objectives Ladder Logic Fundamentals
Electrical Ladder Diagram
Basic Symbols in Ladder Logic
Ladder Logic Programming
Transform
Programming
Basic STOP/START circuit

49. INTRODUCTION
Is an electrical machine diagrams drawn using a standard format
Used to
show the electrical relationship of the components
to speed understanding of how the circuit works

50. OBJECTIVES To describe the basic process of ladder logic
To define terms such as contact, coil, rung, scan, normally open and normally closed in symbols
Simplified ladder logic for simple applications

51. FUNDAMENTALS OF ELECTRICAL LADDER DIAGRAM
Beginning with the control transformer, we add a protective fuse on the left side, which is often part of the transformer itself
From the transformer/fuse combination, horizontal lines are extended to both sides and then drawn vertically down
Control Transformer

52. Structure of a Ladder Diagram
These vertical lines are called power rails or simply rails or uprights
All wires in a control system are numbered
the left rail is often wired as 1
and the right rail is wire number 2 (hot side)
Basic Power Circuit
Power Rail
Power Rail
Rung
Line
Branch
Structure of a Ladder Diagram

53. The voltage difference between the two rails is equal to the transformer secondary voltage
Therefore, any component connected between the two rails will be powered.
Ladder logic program for PLCs is similar to electrical ladder diagrams.
Electrical Ladder Diagram is different from power diagram. Refer to the following Figure
There are some basic rules to follow to make the diagram. Refer Ladder Diagram Rules

54. Ladder Diagram and Power Diagram

55. BASIC OF LADDER LOGIC
Basic symbols found
Contact
Coil

56. CONTACT
Used to represent input conditions to be evaluated by processor to solves program
Two common symbols for contacts
Normally Open ] [
Will not pass current until it is pressed
Normally Closed ]/[
Will allow current flow until it is pressed
When to decide using NO or NC?

57. CASE 1 Think of a doorbell switch. Would you choose the NC switch?
if NC is chosen
Doorbell will continuously ringing until someone pushes the button
So, when is NC used?
24V
Current flow allow bell to ring 0V

58. CASE 2
Previously, we learn that NC is often used when safety is concerned.
Take for example
Production line
Hazardous machine
Always on unless sense object

59. COIL Please Recall ? Represent output
Only appear only on the right side of the rung

60. WIRING TO LADDER DIAGRAM
Switch L1 M
d.c input
Motor ? L2
Wiring diagram
But this wiring is not suitable/relevant
Why? L2 L1
Switch
Motor M
No safety.
Ladder diagram
How to include safety?
BASIC STOP/START CIRCUIT

61. PROGRAMMING
To represent the circuit in in form of ladder logic diagram
we would utilize the power from the rails and simply add the two switches and lamp in series between the rails
Added along are few details
such as wire numbers
reference designators PB1, PB2
L1 for components

62. This wiring scheme is done for safety reasons.
Also note that the switches are on the left, and the lamp is on the right
This wiring scheme is done for safety reasons.
If we put the lamp on the left side and the switches on the right. If there is
a short to ground in the wire from the lamp to the switches 
the lamp would light without either of the switches being pressed

63. For a lamp to inadvertently light is not a serious problem
but assume that instead of a lamp we had the coil of a relay that started the machine
This would mean that a short circuit would start the machine without any warning.

64. By properly wiring the controlled device (called the load) on the right side, a short in the circuit will cause
the fuse to blow when the rung is activated
thus de-energizing the machine controls
and shutting down the machine

65. Rung 2 has two branches on the input side of the rung
It is also possible to have branches on the load side.
For example, we could place another lamp in parallel with LAMP2, thereby creating a branch on the load side

66. It is important to note
it is possible to exchange rungs 1 and 2 without changing the way the lamps operate
This is one advantage of using ladder diagramming. The rungs can be arranged in any order without changing the way the machine operates
It allows the designer to compartmentalize and organize the control circuitry so that it is easier to understand and troubleshoot

67. However, keep in mind that, when beginning PLC ladder programming, the rearranging of rungs is not recommended
since in a PLC, the ordering of the rungs is critical
and it could change the way the PLC program executes.

68. BASIC STOP/START CIRCUITM M M
HOLDING SWITCH
When power is applied, motor coil not energized
When START button is pressed, motor starts
When START released, it remain energized, by the holding contacts.

69. NOTE: Should power fail while the machine is ON
the latch rung will de-energize
When power is restored, the machine will not automatically restart
this is a safety feature that is required on all heavy machines

70. Q & A

71. Ladder Diagram Rules
There are some basic rules to follow when drawing ladder diagrams
to make the diagram easy to read
to provide a properly drawn circuit.

72. Show Only Control Devices Not Power Device
Control device- Switches, Solenoids, Coil and Relays.
Power device- Valves, Motors and Cylinders (these shown separately in power diagram)
Output Devices Located On Right
Output device- Solenoids, lamps and control relays.
Input Devices Located On Left
Input device- Pushbuttons, Limit Switches etc.
All conductor numbered
All rungs numbered

73. All Components Labeled
Functions- i.e. START
Abbreviation i.e. 1PB
At Least one Switch per Line
If no switches- output always be on.
Then does not serve its purpose to control output
Only 1 load per rung
If necessary 2 load;
Never wired loads in series
-Voltage deficient
Loads in parallel
Only Contacts Actually used are Shown