-1- Mitsubishi Melsec PLC Ladder Logic Application -2- Content I. The Structure and Understanding of PLC. The Instruction and History of PLC.▷ Digital Input Module.▷ Digital Output Module.▷ Terminologies of Ladder Logic.▷ The Relationship between PLC Hardware and Software▷ Numeric System of PLC.▷ ▷ Karnaugh Map II. Application Examples for Logical Command. Logical AND▷ Logical OR▷ Logical NAND▷ Logical NOR▷ Logical Exclusive OR▷ 1 Scan-time Oscillator▷ Self-Holding, 0 or 1 Dominant SR/RS Flip-Flop▷ Detect Rising Edge / Falling Edge, Differentiation▷ Dual action Pushbutton▷ Trouble Acknowledge/ Reset▷ III. Application Example for Sequential Command. On Delay / Off Delay Timer▷ One Shot Multi-vibrator▷ Multi-Vibrator▷ Speed Monitor using OFF Delay Timer▷ Preventing Chattering Noise for Mechanical Contacts▷ Finding Stable Value by TIME Filter from Analog Input Hunting▷ Measuring Time for Continuous Production.▷ Optimizing Surveillance Timer of Speed Monitor▷ Surveillance of Motor Drive System▷ Detecting Value Changed▷ -3- IV. Application Example for Flow Sequential Command. Sequence Control with BSFL Command▷ Sequence Control with SFTP Command▷ Call Subroutines and Return Processing▷ Sorting Data of Table in Maximum Order▷ V. Application Example for MUX-DEMUX. Parallel Driving for▷ 7SegmentDisplay Economic Discrete Input Multiplexing-Demultiplexing▷ VI. Application Example for Calculation Command. Analog Input/Output Module▷ A1S68AD/ A1S68DAV,DAI Analog Input Module Set-up▷ Scaling for Analog Input PV▷ Schmitt Threshold ON-OFF▷ Peak Value Hold▷ On / Off Controller for Analog PV▷ Analog Value Clamping, Limitation▷ Bit Shift by Calculation Command▷ Analog Drive Speed Control▷ Finding Stable Value by SUM from Analog Input Hunting▷ Drive Multi-stage Control by Encoder Feedback▷ Ratio Control for Material Mixing▷ Trickle Control for Truck Loading▷ Rate Sampler for Single Counter▷ Analog Scaling for X 0 Shifted Signal▷ Analog Scaling for Y 0 Shifted Signal▷ Piecewise for Proportional Non-Linear Curve▷ Piecewise for Inverse Proportional Non-Linear Curve▷ Linear Profiler▷ -4- VII. Application Example Data Manipulation Command. Clearto0OrSetto1AllBits▷ Set All Bits to 1 by 2's Complement▷ Binary Counter▷ Assembling/ Disassembling of Bits▷ Acceleration/Deceleration Control With Linearity for Set-point▷ Individual ON/OFF Operation by Thumb-wheel Switch Set▷ Ring Counter▷ Display of Trouble Flag Number▷ Que Buffer and First-in/First-out▷ LIFO(Last In First Out) Using Stack Memory▷ Load/Save Data for 2-3 Dimensional Database▷ Data Save/ Sort/ Search for Optimization▷ VIII. Application Example for Computer Link Module. Non-form Communication for Computer Link Module▷ CPU Direct Access via Computer Link Module▷ CPU Access via Dedicated MODEM and Computer Link Module▷ CPU Access via Dial-up MODEM and Computer Link Module▷ Proface GP577R Touch Screen Access via Computer Link▷ Module Fix 32 Access via Computer Link Module▷ Intouch 5.6 Access via Computer Link Module▷ Appendix MODICON Concept Version 2.1 PID Simulation Function Block Diagram▷ Bit Division for MMI Analog tag▷ SIMATIC TI545 PLC PID Simulation▷ SIMATIC TI545 PLC vs Intouch 8.0▷ Modicon E785 PLC vs Intouch 7.1 PID Simulation▷ -5- I. The Structure and Understanding of PLC. The Instruction and History of PLC.▷ Digital Input Module.▷ Digital Output Module.▷ Terminologies of Ladder Logic.▷ The Relationship between PLC Hardware and Software▷ Numeric System of PLC.▷ Karnaugh Map▷ -6- Mitsubishi Melsec PLC Ladder Logic Application The Instruction and History of PLC. 1. Specfication and Unit of PLC. - PLC is an abbireviation of "Programmable Logic Controller". . The existing relay control box can be replaced to PLC. . PLC performs logic solving and circulating beginning and end of program in the memory. - The background of PLC is that, . The end of 1960s, GM(General Motor) Company announced conditions of electronic sequential control equipment proposed to apply to automotive assembly line, and equipment manufacturer developed and distributed sequential control equipment suited to these conditions. - The function of these PLC is that . Sequence control . PID control, Analog control, Positioning control. - Most of PLC has . Basic operation function like AND, OR Contacts and Timer/Counter operation . Practical Application operation like Subroutine, SHIFT, MASTER CONTROL, DATA Calculation. In the beginning, PLC could perform simple control by program as logic controller, high performance function like arithmetic operation, output device control, communication function were added. Also PLC could guarantee and complement high reliability that relay control box couldn't have and flexibility to modify control system. By this way, time and costs to needed to perform inspection, test-run could be minimize and save. After the time, the development of integrated software for the communication between PLC and Computer could make user program easily and provided more familiar environment and ability to build site monitoring using graphic and graphic processing for the data as well as ability to analyze difficult process problem with collected datum and information. Recently PLC are manufactured more compact and lower cost and applied to almost industrial fields. When users control the machine or equipment with PLC, users ought to make a program so that PLC can decide memory content of control algorism. The standards Methods of PLC Programming are presented but there are many differences according to Manufacturers and kinds. IEC 1131-3 (International Electro-technical Commission- Standard for Programmable Controllers-Part 3: Programming Languages) defined international standards of PLC language as belows; - LD(:Ladder diagram) - IL(mnemonic :Instruction List) - SFC(Sequential Function Charts) -7- - FBD(Function Block Diagram) - ST(Structured Text). PLC(Programmable Logic Controller) consists of Input & Output Interface, Memory, Programming terminal, CPU, Power supply structurally. 2. The structure of PLC A. CPU Unit The CPU part of PLC is similar to structure of PC(Personal Computer) and the function are also same. The main part of CPU is consisted as belows; - Micro Processor( CPU) - System Memory - Program Memory - Data Memory. (1) Program method. In-build Program type stores all Sequence Program in the memory and call individually, CPU analyzes and executes program. (2) Control method. - Constant cyclic repetition execution method solves and performs program stored memory from first to end sequentially and return to first. - Interrupt control method solves and performs interrupt execution program when the internal or external interrupt demands. (3) I/O control method First, Processor reads input status from input module, and base on this data, solves logic program from first to end. Finally processor writes results calculated from logic solving to output module. This job processing is called "SCAN". The polling for I/O modules will be indirect method and it should be executed before execution of Program 0 Step. This method is represented as belows; Input Polling Output Processing System Processing LOGIC SCAN -8- (4) Program Command PLC command described in the specification is not for using CPU but for user command designed by PLC manufacturer when user can make sequence program. Each command can be different according to PLC manufacturer but it's not make so much different and function is similar in every PLC's. Program command can be represented to two groups. - Basic Command, Sequence Command : Basic Command is to perform sequence diagram for relay circuits in the PLC, and consisted of basic logical operation command like I/O Command for control signal, AND, OR. - Applied Command : Applied Command provides various functions so that make possible to perform transferring, calculation, comparison, data manipulation and conversion, advanced sequential control program. By using applied command user can save the programming and debugging time, use high speed, high performance function. B. Digital Input Unit Digital input module of PLC is used to get the ON/OFF status from input device. This is mainly used to get information from the machine. For each input device uses different power consumption and different voltage when the pushbutton of operator panel and various kinds of sensor is connected to input module, users should choose suitable input module to each input devices. Digital input module of PLC can be divided to DC input, AC input according to input voltage type and isolated type or non-isolated type. The isolated type is meaning that there exists photo-coupler at input part to isolate external and internal side and this is designed to endure noise in the harsh industrial environment. C. Digital Output Unit Digital Output module of PLC outputs internal ON/OFF status of PLC and operates the machine. Output devices can be connected are mainly lamps, magnet contactor, relays. After magnet contactor(MC) and relay actuators are connected like motor or solenoid valve that can operates the machine. For each output device uses different power consumption and different voltage users should chooses the output module appropriate to output devices. Digital Output module of PLC can be divided to relay output, transistor output, SSR(Solid State Relay) unit according to output contact types. D. Analog Signal Analog value is meaning that physical quantity that varies continuously changing to time like voltage, current, temperature, pressure, flow, velocity. Analog signal can not be connected to computer or PLC that can connect only digital signal. So these physical quantities should coverts to electrical signal like DC voltage, current and convert to digital amount again. Also digital amount PLC inside should convert to analog signal to operate Servo-motor. DC/AC speed control device that can be controlled by analog signal. E. Analog Input Unit (A/D Converter) This is for Analog/Digital conversion Unit and to use analog signal in the CPU. The principal -9- to convert from analog value to digital value is represented as the figure shows that digital value corresponding to analog voltage signal as below. The input voltage range, output bits of A/D converter are different according to kinds. The resolution of AD converter is determined by output bits. The resolution of AD converter is determined by formula as next. Resolution ability = 2 N (N = Output Bit Number) Therefore, The resolution will be larger as larger as output bits and discriminal minimum variation voltage can be expressed as next; Analog voltage range(V) / 2 N ( N = Output Bit Number) For example, when analog input between 0-5V is converted by 8 Bits output, analog input voltage is 2V, we can find digital value, Resolution= 2 8 = 256 If analog input voltage varies from 0V to 5V, output digital value will be varied from 0 to 255. discriminal minimum variation voltage to change Digital value is; V IMIN = 5 / 256 = 0.019531 , and Digital value= 2V / 0.019531V = 102.4 = 102 F. Analog Output Unit (D/A Converter) This unit is for Digital/Analog conversion and used to output analog signal form CPU to outside. The principal to convert from analog value to digital value is that output digital value is corresponded to analog value. The resolution is proportional to the bit numbers to input(2 N ), the output digital value will be converted to analog value from 0V to maximum reference voltage. Let's find analog value corresponding to digital value 102 if analog value is 0-5V voltage, the resolution is 256, the voltage difference is 5V. Therefore the variation of digital 1 results variation of analog signal 0.019531V(5/ 256). and we find 102 x 0.019531V 2 V calculation result. 256 5V2V 102 0V 0 Analog DC Voltage Digital Value -10- G. PID Control Unit PID Control Unit has function of feed-back control so that system output make reference voltage balance and maintain based on deviation between control variable and reference input, recently this control type is mostly used in the industrial facilities. (1) Proportional action - P Action Controller Unit will control to decrease deviation between reference input and process variable. At this time, when operation signal Z(t) is given, and if manipulated amount is gotten, the relationship that manipulated quantities is proportional to operation signal Z(t) is as belows; y(t) = K Z(t) We call this "Proportional action". And K, gain, will determine whether make proportional action strong or weak. If K, gain is high, the process variable will approach to reference signal rapidly, but output can be fluctuated and this result make ill influence to total control stability. On the contrary, if K, gain is low, the process variable will approach to reference signal slowly, and there is possibility to that residual deviation occurs. (2) Integral control action - I Action Integral control action can be represented as action The variation velocity of manipulated value given to control object is proportional to operation signal. Using this factor, we can control integral control action. If integral time is longer, manipulated amount will be small and the time to approach to reference signal is longer. On the contrary, if integral time is shorter, manipulated amount will be large and the time to approach to reference signal is shorter. The relationship of integral control action is as belows; y(t) = K ∫ Z(t) dt The integral control action is not used alone, by combination to P action or D action but can be used to PI, PID action. The integral control action can eliminate residual deviation. If integral time is to short, uncontrolled state can be occurred. (3) Derivative action - D Action Manipulated amount y(t) contributes to operation signal Z(t) by Derivative action. Derivative action calculates manipulated value corresponding to deviation rate so that suppress variation of deviation. The relation ship of derivative action is as follows; y(t) = K dZ(t)/dt Derivative action is not used alone, by combination to P action or D action but can be used to PI, PID action. If derivative action is used to controller, process variable will approach to reference signal rapidly and suppress the fast variation of process variable and external disturbance. (4) PID Control Unit The relationship combined proportional, integral, derivative action described as above, y(t) = K ( Z + 1/Ti ∫ Z(t) dt + Td dZ(t)/dt ) [...]... total program memory size - 20 - Mitsubishi Melsec PLC Ladder Logic Application Relation between PLC Hardware and Software 1 In case of Digital Input Module The how act external electrical excitation to PLC inside ladder logic is represented as next To speak exactly, When we press the push-button switch connected to PLC input module, let' consider what is happened to the PLC internal logic corresponding... the PLC inside, NO(Normal Opened) contact of un-identified X000(not excited because of opening of pushbutton switch) can not make power flow proceed, so this NO contact is electrically OFF state But in the PLC inside, NC(Normal Closed) contact of un-identified X000 can proceed power flow, so this contact is electrically ON state - 21 - P24 PLC External회로 PLC 외부 Circuit PLC Internal Logic Logic PLC. .. push-button switch contact The figure as next is represented before pressing the push-button switch has A contact P24 PLC Internal내부 Logic PLC Logic PLC External 회로 PLC 외부 Circuit X000 Instruction X000 Y010 X000 Power Flow Power N24 Power Rail Left Rail Right The current from power P pole cannot flow to PLC input module address X000 because of opening of pushbutton switch(NO: Normal Open state) in the electrical... Output Module PLC Internal Logic PLC 내부 Logic Instruction X000 X000 PLC External Circuit P24 Y010 Y011 Y010 Power Power Rail Left Rail Right Source Type Digital Output Module Relay 010 Relay 011 Y011 N24 If Y010 Coil Instruction in the PLC internal Logic is Energized, the Relay 010 connected to addressed Y010 of Digital Output Module is also Energized Otherwise if Y011 Coil Instruction in the PLC internal... Status corresponding to PLC corresponding to PLC INPUT point Electrically Dry State Electrically Wet State INPUT point OFF OFF ON ON Contact state in the Possibility to pass PLC Internal Logic the Power Flow NO(Normal NC(Normal NO(Normal NC(Normal - 22 - Open) Close) Open) Close) No Yes Yes No 2 In case of Digital Output Module The how act internal ladder logic variation to PLC outside hardware is... DC input module - 14 - Mitsubishi Melsec PLC Ladder Logic Application Digital Output Module 1 Types of Digital Output Module A Sink Type of Digital Output Module For the Sink Type of Digital Output Module, the current from power source of P pole flows output device like Relay, Solenoid Coil that move Actuators and the load are driven by semi-conductor switching device in the PLC, the common point of... Methods It is commonly demanded the PLC has data exchanges between distributed remote I/O group, different PLC system, high level computer The data link unit can reduce or eliminate I/O points and bulk cable installation, intends to build distributed control, data centralization and management, monitoring system The data link unit has function for data collecting of PLC, extended I/O group M anagem ent... Otherwise if Y011 Coil Instruction in the PLC internal Logic is De-energized, the Relay 011 connected to addressed Y011 of Digital Output Module is also De-energized - 23 - Mitsubishi Melsec PLC Ladder Logic Application Numeric System of PLC 1 Numeric System and DATA The numeric system based on 10(Decimal) is developed naturally and used generally but considering logic system of ON and OFF state, this will... there exists electrical excitation at the X000 and we can say this "Electrically Wet State" In the PLC Logic, NO(Normal Opened) contact of identified X000(excited because of closing of pushbutton switch) can proceed power flow and change to closed state, so this NO contact is electrically ON state But in the PLC inside, NC(Normal Closed) contact of identified X000 can not make power flow proceed and changed... data centralization and management, monitoring system The data link unit has function for data collecting of PLC, extended I/O group M anagem ent L evel C e ll L e v e l F ie ld L e v e l - 11 - Mitsubishi Melsec PLC Ladder Logic Application Digital Input Module 1 Types of Digital Input Module A Digital Input Module of Sink Type For the digital Input Module of Sink Type, the current driving input point . between PLC Hardware and Software▷ Numeric System of PLC. ▷ Karnaugh Map▷ -6- Mitsubishi Melsec PLC Ladder Logic Application The Instruction and History of PLC. 1. Specfication and Unit of PLC. - PLC. TI545 PLC PID Simulation▷ SIMATIC TI545 PLC vs Intouch 8.0▷ Modicon E785 PLC vs Intouch 7.1 PID Simulation▷ -5- I. The Structure and Understanding of PLC. The Instruction and History of PLC. ▷ Digital. -1- Mitsubishi Melsec PLC Ladder Logic Application -2- Content I. The Structure and Understanding of PLC. The Instruction and History of PLC. ▷ Digital Input Module.▷ Digital