PLC PROGRAMMING CHAPTER 4 PROGRAMMING. Provide an overview of PLC programming method using programming languages commonly used.

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1 CHAPTER 4 PROGRAMMING Main Objective: Provide an overview of PLC programming method using programming languages commonly used. Specific Objectives: After completed this chapter, student will know the major component 1. Familiarise with the PLC Programming system 2. Able to explain PLC programming method using Ladder Diagram and mnemonic code., Instruction set and logic function. 3. Understand and use Ladder Diagram and mnemonic code to solve control systems circuits. 4. Explain the following logic instruction set: Load. Load Not, Out, And, And Not, Or, Or Not, And Ld and Or Ld. 5. Explain sequential instruction set: No Operation, End, Interlock, Jump, Keep, Set/Reset and Differential Up/Down. 6. Explain the timer and Counter instruction set and execute timer/counter application solution methods. 4.0 Introduction PLC programming process is to plan activities such as design and write a program to perform the required tasks. Here are the parts that should be there in a PLC program. Start Operating Mode The Reset Operations / Ordering Process Signal Output Status Output End Starting an operation Determining the origin of the device input / output and also the starting point Controlling the operation of start / stop it manually or automatically in the program Program design as required by the task Trigger output devices. Display indicator light or alarm. Stop the process./operation SARIATI Page 1

2 4.1 Programming Language IEC is the international standard for programmable controller programming languages. The following is a list of programming languages specified by this standard: i. Ladder Diagram (LD) ii. Instruction List (IL) iii. Structured Text (ST) iv. Sequential Function Chart (SFC) v. Function Block Diagram (FBD) One of the primary benefits of the standard is that it allows multiple languages to be used within the same programmable controller. This allows the program developer to select the language best suited to each particular task. i. Ladder Diagram Ladder Diagram is kind of graphical programming language that changed the relay control wiring circuit diagram. Ladder Diagram contains tracks from left to right contact diagram (see Figure below). This platform is connected to contact elements available normally open - NO or available Normally closed - NC through the current path and loop elements. Ladder diagram also shows the control circuit and the display function and a combination of the sequence of operations for each branch of the horizontal lines separately. +ve INPUT CONDITION OUTPUT ACTION -ve NO NC Ladder Diagram Mnemonic Instruction There are other methods to program PLCs. One of the earliest techniques involved mnemonic instructions. These instructions can be derived directly from the ladder logic diagrams and entered into the PLC through a simple programming terminal. ii. Instruction List This low-level language is similar to Assembly language and is useful in cases where small functions are repeated often. Although it is powerful, it is considered to be difficult to learn. SARIATI Page 2

3 Example Calculate new weight by subtracting tare weight from net weight. LD weigh_command JMPC WEIGH_NOW ST ENO RET WEIGH_NOW: LD gross_weight SUB tare_weight iii. Structured Text Structured Text (ST) is a high level textual language that is a Pascal like language. It is very flexible and intuitive for writing control algorithms. Structured Text uses operators such as logical branching, multiple branching, and loops. People trained in computer programming languages often find it the easiest language to use for programming control logic. When symbolic addressing is used, ST programs resemble sentences, making it highly intelligible to beginner users as well. ST is ideal for tasks requiring complex math, algorithms or decision-making. Its concise format allows a large algorithm to be displayed on a single. Benefits of Structured Text People trained in computer languages can easily program control logic Symbols make the programs easy to understand Programs can be created in any text editor Runs as fast as ladder Example 1 We have Motor that will be controlled manually by 2 push buttons (Start Push Button, and Stop Push Button). When the Start Push Button is pushed then the Motor will be turned ON. and when the Stop Push Button is Pushed then we want to stop the Motor. (Security logic has been taken o ff this logic, for the purpose of domonstration.) IF StartPb THEN Motor := 1; END_IF; IF StopPb THEN Motor := 0; END_IF; SARIATI Page 3

4 iv. Sequential Function Chart These are similar to flowcharts, but much more powerful. This method is much different from flowcharts because it does not have to follow a single path through the flowchart. SFC programming offers a graphical method of organizing the program. The three main components of an SFC are steps, actions and transitions. Steps are merely chunks of logic, i.e., a unit of programming logic that accomplishes a particular control task. Actions are the individual aspects of that task. Transitions are the mechanisms used to move from one task to another. Control logic for each Step, Action and Transition is programmed in one of the other languages such as Ladder Diagram or Structured Text. Is a kind of graphic language (see Figure 4.1.4). Elements are the steps, transitions, choice and parallel branch. Each step shows the status of the control program processes the active or inactive. One step consists of action based on the transition. The action consists of the sequence structure itself. Step 1 MOTOR (Start) Transition 1 Action Step 2 MOTOR (Stop) Transition 2 Step 3 Sample Program In Sequencial Function Chart Language v. Function Block Diagram Like SFC, FBD is a graphical language that allows programming in other languages (ladder, instruction list, or structured text) to be nested within the FBD. In FBD, program elements appear as blocks which are "wired" together in a manner resembling a circuit diagram. FBD is most useful in those applications involving a high degree of information/data flow between control components, such as process control. SARIATI Page 4

5 4.1.1 Basic Ladder Diagram A ladder diagram consists of a vertical line on the left and right are called bus bars and horizontal lines to the right, called the instruction lines. Along the lines of command are logical combinations of conditions (conditions) that will determine when and how the instructions on the right at all to be implemented. Based on the picture above, one should note that a ladder diagram consists of two basic parts: left section also called conditional, and a right section which has instructions. When a condition is fulfilled, instruction is executed. Example Ladder Diagram as shown in figure below instruction Sample Ladder Diagram SARIATI Page 5

6 The pairs of vertical lines along the branch line is called the conditions. These conditions consist of two, namely: i. Normally open condition (NO) ii. Normally closed condition (NC) The numbers in each case to determine the bit operations per instruction. Each command in ladder diagram either ON or OFF depending on the status of specified bit operations. Notes: Normally open condition is ON if the bit operation is ON and will be OFF if the bit operation is OFF. Normally closed condition is ON if the bit operation is OFF and will be OFF if bit operation is ON Normally Open Normally Closed Instruction n Instruction n Instruction executed when the IR bit is ON Instruction executed when the IR bit is OFF Example of Ladder Diagram 4.2 Basic Terms Execution Conditions Logical combination of the ON and OFF states gathered to establish an instruction to be implemented. This condition is called Execution Condition. Refer to figure below instruction Examples of Execution Conditions Instructions will be in the Execution Conditions ON when IR is ON, IR is OFF and IR is ON. SARIATI Page 6

7 4.2.2 Operand Bits Bit operations for each instruction can consist of any of the bits in the memory area IR, SR, HR, TC or TR. This means that the conditions in Ladder Diagram can be determined by the bit I / O, flags, work bits, timer / counters and others. Table shows the memory map refers to the PLC type SYSMAC OMRON-CQM1H. DATA AREA BIT FUNCTION Input IR Used as the input bit IR Area Area IR01515 Output Area Work Area IR10000 IR11515 IR21600 IR21915 used as output bits. Bit has no function specifically. Can be used freely in the program SR Area SR24400 SR25507 This bit use to do certain functions, such as flags (flags) and control bits. TR Area TR 0 TR 7 This bit is used to temporarily store the status ON / OFF on the branches of the program HR Area HR 0000 HR 9915 This bits used to store data and maintain the status ON / OFF when the power is off. Timer/Counter Area TC 000 TC 511 The same number used for the timer and counter. Use for TC000 to TC002. `interval timer ' SARIATI Page 7

8 4.2.3 Logic Block The respond to an instruction is determined by the relationship between the conditions on the instruction line that connects them. Any group of conditions that formed to produce a logical result is called a logical block. Refer to Figure instruction Example Logic Block Instruction Block A block of instruction is composed of all the instructions contained in a block. Block is obtained by drawing a horizontal line without cutting a vertical line and vice versa. Refer to Figure Ladder diagram can not be read by the Programming Console. Thus the ladder diagram should be changed to mnemonic code. Mnemonic code provides the same information as ladder diagram and can be typed directly on Programming Console. ADDRESS INSTRUCTION OPERASI / DATA OR AND AND LD OUT TIM 000 # CNT 002 # FUN 01 Example SARIATI Page 8

9 ANSWER ALL THESE QUESTIONS 1. What do you understand about Ladder Diagram and draw one (1) example of a Ladder Diagram. 2. Explain the purpose of the following terms: i. The logic blocks ii. The Instruction block Reference; 1. SARIATI Page 9

10 UNIT 5: BASIC INSTRUCTIONS SET OBJECTIVE: Describe the set of instructions used in PLC programming SPECIFIC OBJECTIVES: At the end of this unit student should be able to: i. Know the functions of the instruction LOAD, LOAD NOT, OUT, AND, AND NOT, OR, NOT and OR END ii. Know the function block instruction AND LD and OR LD. iii. Convert Ladder diagram to. NOTE: These instructions will be explained later is based on OMRON PLC brands SYSMAC CQM1H 5.0 Introduction There are a lot of instructions used to develop the PLC program. Each instruction has a respective function. 5.1 LD - LOAD Instruction These instructions are use to start a line of the program. It is used in the first contacts in the normally open condition (NO). Ladder Diagram instruction Address Instruction Operand/Data instruction Explanation: The Execution Conditions of the instruction on the right will be ON when IR is ON. SARIATI Page 10

11 5.2 LD NOT - LOAD NOT Instruction PLC PROGRAMMING These instructions are use to start a line of the program. It is used in the first contacts in the normally closed condition (NC). Ladder Diagram instruction Address Instruction Operand/Data LD NOT instruction Explanation The Execution Conditions of the instruction on the right will be ON when IR is OFF 5.3 AND - AND Instruction These instructions are used in the second contact in a normally open (NO) and a series with previous contacts Ladder Diagram Address Instruction Operand/Data instruction AND instruction Explanation The Execution Conditions of the instruction on the right will be ON when IR and IR are ON SARIATI Page 11

12 5.4 AND NOT - AND NOT Instruction These instructions are used in the second contact in a normally closed (NC) and in series with previous contacts Ladder Diagram Address Instruction Operand/ instruction Data n AND NOT instruction Explanation The Execution Conditions of the instruction on the right will be ON when IR ON and IR are OFF. 5.5 OR - OR Instruction These instructions are used in the second contact in a normally open (NO) and in line (parallel) with previous contacts.. Ladder Diagram instruction n Address Instruction Operand/Data OR instruction Explanation The Execution Conditions of the instruction on the right will be ON when either IR or IR are ON. SARIATI Page 12

13 5.6 OR NOT - OR NOT Instruction PLC PROGRAMMING These instructions are used in the second contact in a normally closed (NC) and in line (parallel) with previous contacts Ladder Diagram Address Instruction Operand/Data instruction n OR NOT instruction Explanation The Execution Conditions of the instruction on the right will be ON when either IR is ON or IR is OFF or IR ON, IR OFF simultaneously 5.7 OUT - OUTPUT Instruction These instructions are used for the coil output. Ladder Diagram Address Instruction Operand/ Data OUT IR will ON when IR is ON. 5.8 END END instruction has no physical contact device. It is the last instruction required for completion of a program. If no END instruction, the program cannot be implemented SARIATI Page 13

14 Ladder Diagram Address Instruction Operand/ Data END AND NOT OUT FUN 01 For PLC type OMRON - SYSMAC CQM1H, the instruction FUN 01 is the END instruction. 5.9 OR LD - BLOCK LOGIC OR Instruction The OR LD instruction has no physical contact device. Only a programming tool for solving complex OR function as a series of contacts LD (or LD NOT), in parallel with a series of other contacts. Ladder Diagram Address Instruction Operand/Data END AND LD AND OR LD OUT FUN 01 SARIATI Page 14

15 5.10 AND LD - BLOCK LOGIC AND Instruction The AND LD no physical contact device. Only a programming tool for solving complex functions such as AND connects a number of OR, OR NOT, OR LD in the series. Ladder Diagram END Address Instruction Operand/ Data OR LD OR AND LD OUT FUN OR LD and AND LD When both logic block instruction is to be used in Ladder Diagram, a program must be written from the bottom up to merge logic blocks. For example, ladder diagram below: Logic block of instruction for the last two blocks (blocks b1 and b2 blocks) are written first and then followed by the first logic block instruction (block a). SARIATI Page 15

16 Ladder Diagram Block b Block a Block b2 END Address Instruction Operand/Data LD NOT AND Block a LD AND NOT Block b LD NOT AND OR LD AND LD Block b2 Block b2 + Block b1 = Block b Block b, Block a OUT FUN 01 Example. SARIATI Page 16

17 UNIT 6 (4.3) : SEQUENTIAL INSTRUCTION SET Objective Describe the sequence instruction set NO OPERATION, END, INTERLOCK, JUMP, KEEP, SET / RESET and DIFFERENTIATE UP / DOWN Specific Objectives: At the end of this unit you should be able to understand set of instructions the following sequence: NO OPERATION END INTERLOCK JUMP KEEP SET/RESET DIFFERENTIATE UP / DOWN 6.0 Introduction In this unit you will be exposed to a sequence of instructions which usually acts as the last instruction in the instruction line. Instruction sequence SET, RESET, KEEP, DIFFERENTIATE UP, DOWN DIFFERENTIATE, used to ON and OFF state output bits in the IR. These instructions are used to control the status of the other bits in the IR or in other areas. INTERLOCK instruction sequences can overcome the problem of storing execution conditions, in the branches of the ladder diagram. JUMP instruction sequence can be used to control devices that require a product that can last a long time. 6.1 NO OPERATION NOP ( 00 ) These instructions do not have a ladder diagram symbols and will not do any operations. When you remove the memory in this instruction will be displayed on the console screen PLC programming. SARIATI Page 17

18 6.2 END END(01) Acting as the last instruction for each program (see figure 6.2) There is no instruction will be written after the END instruction (01) implemented. If there is no END instruction (01) in the program, the task would not be implemented and verse NO END LIST is displayed on the programming PLC console screen END Ladder Diagram shows the END instruction Address Instruction Operand/Data LD NOT OUT FUN(01) 6.3 INTERLOCK [ IL ( 02 ) ] DAN INTERLOCK CLEAR [ ILC ( 03 ) ] IL (02) and ILC (03) must be used together. These instructions are used to solve the problem of storing execution conditions at branch points. When the INTERLOCK instruction is ON as shown in Ladder Diagram 6.3, the implementation of the INTERLOCK instruction will control all of the instruction execution until the instruction INTERLOCK CLEAR. When the INTERLOCK instruction is OFF, INTERLOCK CLEAR instruction will reset the program operation. To set the INTERLOCK instruction for PLC tpe OMRON - SYSMAC CQM1H is FUN 02 for INTERLOCK instruction and FUN 03 is INTERLOCK CLEAR instruction. SARIATI Page 18

19 00000 IL (02) ILC (03) END Figure 6.3 : Ladder Diagram shows IL ( 02 ) dan ILC ( 03 ) instruction Address Instruction FUN LD OUT FUN FUN 01 - Operand/Data Referring to Ladder Diagram 6.3, When the instruction input LD is ON, the instruction IL (02) will be ON. Instruction output OUT will depend on the instruction input ON LD and LD If the input instruction LD ON, output OUT will be ON. If the input instruction LD OFF, output OUT will be OFF. In the event that the input instructions LD OFF, instruction IL (02) is OFF. Instructions to the output OUT will be OFF. Next program ILC (03) will reset the program. SARIATI Page 19

20 Refer the table below: Instructions LD IL(02) ON OFF Instructions LD Input ON OFF ON OFF Instructions OUT Output ON OFF OFF OFF 6.4 JUMP [ JMP (04) ] DAN JUMP END [ JME (05) ] Instructions JMP (04) is usually used in pairs with the command JME (05) for the jump. JMP (04) is a command to determine the starting point of the jump and JME (05) is the instruction that the direction of the jump.( where to jump). When the instruction JMP (04) is ON, no jump will occur and the program will be implemented as written. When the instruction JMP (04) is OFF, a jump to the instruction JME (05) which has the same number will be done. Further instructions are the instructions JME (05) will be implemented. Instructions JUMP and JUMP END can use the numbers from the range of 00 to 99. To set the instruction for PLC type OMRON - SYSMAC CQM1H, is FUN 04 for JUMP instruction and FUN 05 instruction is the JUMP END instruction JMP (04) JME (05) 01 END Figure 6.4 : Ladder Diagram shows JUMP instruction SARIATI Page 20

21 Address Instruction FUN (04) LD OUT FUN (05) FUN (01) - Operand/Data Referring to Ladder Diagram 6.4, When the input instruction LD is ON, instruction JMP (04) will be ON. Subsequent instructions will be implemented as written. If the input instruction LD is ON, output instruction OUT will be ON. If the input instruction LD is OFF, output instruction OUT will be OFF. When the input instruction LD is OFF, instruction JMP (04) will be OFF. Next jumps to Instruction JME (05) will occur. All instruction that is between JMP (04) and JME (05) will be ignored. Refer to the table below. Instruction LD JMP(04) ON Instruction LD Input ON Instruction OUT Output ON OFF OFF OFF Not implemented/executed Not implemented/executed SARIATI Page 21

22 6.5 KEEP KEEP (11) KEEP instruction is used to maintain the status bit operation based on two state execution condition. KEEP (11) operates like a Latching Relay which is set by S and reset by R. When S is in the ON state, the operation of a particular product instruction is ON and remain ON until reset, regardless of whether S is ON or OFF. When R is in the ON state, the operation of a particular product instruction is OFF and remain OFF until reset, regardless of whether R is ON or OFF. For PLC type OMRON - SYSMAC CQM1H, the instruction FUN 11 is KEEP instruction HR0000 S R KEEP (11) HR END Figure 6.5 : Ladder Diagram shows KEEP instruction Address Instruction Operand / Data LD LD FUN (11) HR LD HR OUT FUN (01) SARIATI Page 22

23 With reference to Figure 6.5, Instruction LD acts as S (Set)-and the LD acts as R (Reset). When the instruction LD ON, the output instruction OUT will be ON and will remain ON even if the instruction LD is OFF. When the instruction LD ON, then the output OUT instruction OFF and will remain OFF even though the instruction LD in OFF or ON state. Instruction LD Reset OFF ON Instruction LD Set ON OFF ON OFF Instruction OUT Output ON ON OFF OFF 6.6 SET and RESET SET and RESET instruction will change the status of bit operations only when the implementation is ON. In the OFF condition, the instructions will not change the bit operation status SET RESET Figure 6.6 : Ladder Diagram shows the Set and Reset instruction SARIATI Page 23

24 Address Instruction Operand / Data SET LD RESET Referring to Ladder Diagram 6.6, When the input instruction LD is ON, SET instruction command to ON and always ON regardless of whether the input instruction LD is ON or OFF. When the inputs instruction LD is ON, RESET instruction is ON and SET instruction will be off. Its operations can be understood clearly in the KEEP instruction. 6.7 DIFFERENTIATE UP [ DIFU (13) ] DAN DIFFERENTIATE DOWN [DIFD (14) ] DIFU instructions (13) and DIFD (14) will ON the output within a very short time. Instructions DIFU (13) will turn the output to ON when the input signal changes from OFF to ON. Instructions DIFD (14) will turn the output to ON when the input signal changes from ON to OFF. For PLC type of OMRON - SYSMAC CQM1H, instruction FUN 13 is instruction DIFFERENTIATE UP and FUN 14 is instruction DIFFERENTIATE DOWN. Input DIF U DIF D SARIATI Page 24

25 DIFU (13) 01OOO END Figure 6.7a : Ladder Diagram shows DIFFERENTIATE UP instruction Address Instruction Operand / Data FUN (13) LD OUT Referring to Ladder Diagram 6.7a, When the input instruction LD is ON (has changes from OFF to ON), operand bit will be ON, the output OUT will be ON within a very short time and then OFF. We can not see the situation in the products. After that the operand bit will be OFF regardless of the status of the input instruction LD DIFU (14) 01OOO END Figure 6.7b : Ladder Diagram shows the DIFFERENTIATE DOWN instruction SARIATI Page 25

26 Address Instruction Operand / Data FUN (14) LD OUT Referring to Ladder Diagram 6.7b, When the input instruction LD is OFF (change from ON to OFF), operand bit will be ON, the output OUT will be ON within a very short time and then OFF. We can not see the situation in the products. After that the operand bit will be OFF regardless of the status of the input instruction LD SARIATI Page 26

27 UNIT 7(4.4) : TIMER AND COUNTER OBJECTIVE: Describe the instruction set of timer and counter. SPECIFIC OBJECTIVES: At the end of this unit you should be able to: 1. Describe the instruction timer (TIMER TIM) 2. Describe the instruction counter (COUNTER - CNT). 3. Converts Ladder Diagram to mnemonic code. 7.0 Instruction TIMER (TIM) and COUNTER (CNT) is the instructions that require numbers TIM / CNT (N) and the set value(sv). The range of numbers TIM / CNT is from 000 to 511, while the range of set values for the TIM / CNT is 0000 to 9999 The numbers TIM / CNT can not be used twice. When a number has been used as definer, such as number 000 for instructions on TIM / CNT, the number can not be used again. When a number is defined as the number of TIM / CNT, it can be used as often as required as an operator operand in other instructions from the command TIMER or COUNTER. 7.1 TIMER - TIM Symbol TIM N SV Timer numbers (N) is between 000 and 015. The set value (SV) is between 0000 to All numbers TIM / CNT can be used as definer in only one TIMER or COUNTER instruction. SARIATI Page 27

28 Example TIMER is enabled/activated when the execution condition is ON and will be reset to set value (SV) when the execution condition is OFF. The set value (SV) of TIMER is the BCD between # 0000 to # For example, if TIMER be set to 5 seconds, then the set value (SV) is # Ladder Diagram Tim 000 # 0050 TIM END Address Instruction Operand/Data TIM 000 # LD TIM OUT FUN 01 Operating Condition: When the input (LD 00000) is ON, the timer contact will be activated after 5 seconds. Next the output (OUT 10000) will be ON SARIATI Page 28

29 Example Ladder Diagram Tim 000 #0050 TIM TIM END Address Instruction Operand/Data TIM 000 # LD TIM OUT LD NOT TIM OUT FUN 01 Operating Condition: When the input (LD 00000) ON, the timer (TIM 000) will be activated after 5 seconds and the output (OUT 10000) will be ON. While the output (OUT ) will be ON as soon as the supply is supplied and will be OFF after 5 seconds. Timer will continue to be active as long as the input state is ON. SARIATI Page 29

30 Example Ladder Diagram Tim 000 # 0050 TIM 000 TIM Tim 001 # 0030 END Address Instruction Operand/Data TIM 000 # LD TIM AND NOT TIM OUT LD TIM 001 # OUT FUN 01 SARIATI Page 30

31 Operating Condition: When the input (LD 00000) ON, the timer (TIM 000) will be activated after 5 seconds. Next the output (OUT 10000) will be ON. After 3 seconds the output (OUT 10000) ON, the timer (TIM 001) will be activated the next output (OUT 10000) will be OFF and the timer (TIM 001) will be OFF. When the timer TM001 OFF, contact TIM 001 (NC) will be ON and the output (OUT 10000) is ON state. Output (OUT 10000) will continue ON and OFF until the input (LD 00000) in the OFF state. 7.2 COUNTER - CNT Symbol CP R CNT N Number TIM / CNT can be used as definer for either timer or counter. Counter numbers are range from 000 to 015. Counters are used to calculate the count down from the set value (SV) on the execution condition on the counting pulse (CP) when it is changed from OFF to ON. The set value (SV) is range 0000 to Counters will reset to the reset (R). Ladder Diagram CNT 001 CP R CNT 001 # END SARIATI Page 31

32 Address Instruction Operand/Data LD CNT 000 # LD CNT OUT FUN 01 Operating Condition Counter set to count 10. When the input (LD 00,000) is the pulse of ten, a counter will be activated and thus the output (OUT 10000) will be ON. When reset (LD 00,001) ON, a counter will be in original condition SARIATI Page 32

33 7.3 The Application Of Timer And Counter Instructions The number of Counter cannot be the same number to the number of timer because both share the same data in the PLC memory CP 0000 R CNT 000 # 0005 CNT TIM 001 # 0050 TIM END Operating Condition: Counter set to count 5. When the input (LD 00,000) is the pulse of five, a counter will be activated and thus the output (OUT 10000) will be ON. When the output (OUT 10000) ON, TIM 001 will be activated after 3 seconds and then the output (OUT ) will be ON. Both the output (OUT 10000) and (OUT ) will always be ON until reset (LD 00001) in the ON state. Reset will return the counter to its original condition. SARIATI Page 33