1. PLC PROGRAMMING

2. PLC Programming Languages
The standard IEC (International Electro technical Commission) was established to standardize the multiple languages associated with PLC programming by defining the following five standard languages:
• Ladder Diagram (LD) —a graphical depiction of a process with rungs of logic, similar to the relay ladder logic schemes that were replaced by PLCs.
• Function Block Diagram (FBD) —a graphical depiction of process flow using simple and complex interconnecting blocks.
• Sequential Function Chart (SFC) —a graphical depiction of interconnecting steps, actions, and transitions.
• Instruction List (IL) —a low-level, text-based language that uses mnemonic instructions.
• Structured Text (ST) —a high-level, text-based language such as BASIC, C, or PASCAL specifically developed for industrial control applications.

3. Ladder Diagram and Programming:
Load: The load (LD) instruction is a normally open contact
A Load (contact) symbol
Load Bar: The Load Bar instruction is a normally closed contact.
A Load Bar (normally closed contact) symbol
An OUT (coil) symbol
Out :The Out instruction is sometimes also called an Output Energize instruction. The output instruction is like a relay coil

4. matrix limitation diagram for a typical PLC.
A maximum of seven parallel lines and 10 series contacts per rung is possible.

5. Addressing format

6. Logic elements

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

9. You can use a personal computer as a programming device

10. Instructions Timers Counters Master control Jump control Data handling
Shift registers

11. TIMERS In general, there are three different PLC timer types:
On-delay timer (TON)
Off-delay timer (TOF)
Retentive timer on (RTO)

12. ON-DELAY TIMER (TON)
An on-delay timer is used when you want to program a time delay before an instruction becomes true.

13. Contd..

14. OFF-DELAY TIMER (TOF) and RETENTIVE TIMER ON (RTO)
The off-delay timer (TOF) operation will keep the output energized for a time period after the rung containing the timer has gone false.
A retentive timer (RTO) accumulates time whenever the device receives power, and it maintains the current time should power be removed from the device.

15. OFF-DELAY TIMER (TOF)

16. RETENTIVE TIMER ON (RTO)

17. COUNTERS

18. UP-COUNTER

19. Contd..

20. DOWN-COUNTER
The down-counter instruction will count down or decrement by 1 each time the counted event occurs.
Each time the down-count event occurs, the accumulated value is decremented.

22. MASTER CONTROL

23. JUMP CONTROL

24. DATA HANDLING INSTRUCTIONS
Moving data
Comparison of magnitude of data( greater than, equal to, less than)
Arithmetic operation (Addition & subtraction)
Conversion between binary coded decimal, binary, octal.

25. MOVE INSTRUCTION

26. DATA COMPARISON EQUAL TO NOT EQUAL TO GREATER THAN
GREATER THAN OR EQUAL

27. DATA COMPARISON
LESS THAN
LESS THAN OR EQUAL
LIMIT TEST

28. ARITHMETIC OPERATION
ADDITION
SUBTRACTION
MULTIPLICATION
DIVISION

29. TO BINARY CODED DECIMAL FROM BINARY CODED DECIMAL
CONVERSION
TO BINARY CODED DECIMAL
FROM BINARY CODED DECIMAL
The convert to BCD (TOD) instruction is used to
convert 16-bit integers into binary-coded decimal (BCD) values.
The convert from BCD (FRD) instruction is used to convert binary-coded decimal (BCD) values to integer values.

30. BIT SHIFT REGISTERS
A bit shift register is a register that allows the shifting of bits through a single register or group of registers.
The bit shift register shifts bits serially (from bit to bit) through an array in an orderly fashion.
A shift register can be used to simulate the movement , or track the flow, of parts and information
Common applications for shift registers include the following:
Tracking of parts through an assembly line
Controlling of machine or process operations
Inventory control
System diagnostics

31. Data in the shift register could represent the following:
• Part types, quality, and size
• The presence or absence of parts
• The order in which events occur
• Identification numbers or locations
• A fault condition that caused a shutdown

32. ANALOG I/O MODULES
Discrete devices are inputs and outputs that have only two states: on and off.
In comparison, analog devices represent physical quantities that can have an infinite number of values.
Typical analog inputs and outputs vary from 0 to 20 milliamps, 4 to 20 milliamps, or 0 to 10 volts.

33. Contd..
The analog input interface module contains the circuitry necessary to accept an analog voltage or current signal from the level transmitter field device.
This input is converted from an analog to a digital value for use by the processor.
The circuitry of the analog output module accepts the digital value from the processor and converts it back to an analog signal that drives the field tank level meter.
Common physical quantities measured by a PLC analog module include temperature, speed, level, flow , weight, pressure, and position.

34. Contd..
For example, a sensor may measure temperature over a range of 0 to 500°C, and output a corresponding voltage signal that varies between 0 and 50 mV.

35. Selection of PLC Input/output capacity  Future?
Types of Input / Output required
Size of memory
Speed and power of CPU

36. Areas of Application Manufacturing/Machining Food/beverage Metals
Power
Mining
Petrochemical/Chemical

37. Examples of PLC Programming Softwares:
1.Allen-Bradley – Rockwell Software
RSLogix 500
2. Modicon - Modsoft
3. Omron - Syswin
4. GE-Fanuc Series 6 – LogicMaster6
5. Square D- PowerLogic
6. Texas Instruments – Simatic
7. Telemecanique – Modicon TSX Micro