NEAR EAST UNIVERSITY. Faculty of Engineering

Transcription

1 NEAR EAST UNIVERSITY Faclty of Engineering Department of Electrical and Electronic Engineering CONVEYOR SYSTEM CONTROL BY PLC Gradation Project EE-400 Stdent: Necip Faz1I Battal ( ) Spervisor: Ozgr Cemal Ozerdem Lefkosa

2 ACKNOWLEDGEMENTS First and Foremost I wold like to thank almighty ALLAH/or giving me the strength and sincereness dring this Project. Special thanks to my spervisor Ass. Prof Dr. Ozgr Cemal GZERDEM, for his valable advice and otmost spport in completing this project. He always helped me a lot and!felt remarkable progress dring my project preparation. Also I wold like to thank to him for giving his time dring my stdy and my advisering. I wold like to thank to Sahin BAYRAK, Ysf DEMjRESjK and Levent Hamdi UYGUN for their help and spirital spport dring my bachelor stdy. I also wold like to thank to all my friends and specially Kadir TOK, Fatih GUNDE, Nrllah SEZjK, Hakan AYAN, Senol KO<;, Nader SAMEER and Bashar JALAL who spported and helped me all the time. I never forget my wonderfl times that I spent in Cyprs and Near East University with my good friends. Last bt not least, I wold like to express my greatest thanks to my family, especially my parents for being patientfll dring my ndergradate degree stdy. I cold never have completed my stdy withot their encoragement and endless spport. Necip Fal BATTAL

3 ABSTRACT Prodction process has become easier with PLC se in today's indstry. PLC technologies offer a wide variety of featres inclding, advanced programming techniqes, special commnication capabilities, flexible atomation soltions and many other important featres. Today's PLCs offer faster scan time; ergonomical strctre with space efficient, power saving design and large nmber of inpts/otpts. Modem PLC technology offers commnication with other control systems; it also provides recognition of failres and diagnosis of errors and special commnication protocols for PLC field devices interface. In this project, conveyor system atomation is realized with 12VDC motors, signal lamps, start/stop bttons and 24VDC diffse reflective type photoelectric sensors. Therefore, CPU inpts, 6 otpts (24VDC inpt/otpt type) PLC is sed depending on the types and the nmber of inpts/otpts. Conveyor System is performed and the indicator lamps, DC motors and sensors are operated physically with indstrial considerations sing the Programmable Logic Controller (PLC). DC motors are driven and controlled by 24VDC type relays. 11

4 CONTENTS ACKNOWLEDGEMENTS ABSTRACT CONTENTS INTRODUCTION 1 PLCs and PLC TYPES 1.1 What is a PLC? 1.2 PLC History 1.3 Why Use PLCs? Vl Types of PLC 1.4.a Compact PLCs 1.4.b Modlar PLCs 1.5 PLC Configrations and Selection 1.5.a Micro PLCs 1.5.b Medim PLCs 1.5.c Large PLCs PLC INTERNAL STRUCTURE & PROGRAMMING TECHNIQUES 2.1 How a PLC Operates? 2.2 Central Processing Unit The Inpt Interface System a The Inpt Interface Configration The Otpt Interface System a The Otpt Interface Configration Memory Power Spply 2.3 Commnication in PLCs Internal Commnication a Data Bs b Address Bs c Control Bs

5 2.3.2 External Commnication a The RS-232 Protocol b Fieldbses PLC Operation Principle PLC Programming Langages a Ladder Langage b Boolean Langage Introdction to PLC Programming Siemens S7-200 PLCs a Mode Switch and Analog Adjstment b Inpts c Otpts Timers a On-Delay Timer (TON) b Retentive On-Delay (TONR) Conters a Up Conter b Up/Down Conter(CTUD) Compare Instrctions b Compare Word Integer 36 3 INDUSTRIAL APPLICATIONS & CONVEYOR 38 CONTROL SYSTEMS 3.1 Introdction to Control Systems Control System Devices Electrically Controlled Switches a Contactors b Relays Fses a Miniatre Circit Breakers(MCB) Psh Bttons a Start Btton b Stop Btton c Two -Way Btton Signal Lamps 43 lv

6 3.3 Sensors Sensor Characteristics/Specifications a Sensing Distance b Hysteresis 3.3. l.c Repeatability 3.3. l.d Switching Freqency e Response Time Sensor Power Ratings Sensor Otpt Configration a Transistor Otpt Indctive Proximity Switches Capacitive Proximity Switches Photoelectric Sensors 3.4 Brshed DC Motor Stator Rotor Brshes and Commtator 3.5 Conveyor Carrying System Application 3.5.a Conveyor Operation and Control 3.5.b Ladder Logic Program 3.5.c Network Explanations CONCLUSION REFERENCES APPENDICES Appendix Diffse Reflective Type Photoelectric Sensor Datasheet Appendix 2 Conveyor System Drawings Appendix 3 Cost Calclation of Project V

7 INTRODUCTION Indstrial Revoltion has played a vital role in hman life and it changed hman perspective towards the world. Hman expectations, needs, ideas, relations, life style, etc. have changed. Easy, qick, economic, ergonomic, portable and smart things have become poplar all over the world. Technology was commented as an answer to hman expectations and a hge market for trade. Prodction Management and Qality Control has become the most important concern to increase in prodctivity and redce the nit cost of a prodct. Flexible systems are being replaced with blk, complex and expensive systems. Imagine an atomobile prodction factory where hndreds of cars are being prodced and many seqential processes are reqired in prodction period. Prodction failre is a fatal error and for every second, company is loosing money becase workers are employed bt they cannot perform their tasks and orders are not prepared on time. Usally, problems are not simple. It is not easy to find the problem in a very complicated system. For example, a problem occrred in the robot arm of a conveyor belt. This robot signal flows and electrical energy transfer is distribted/controlled by a control panel. The problem may be related with internal part of robot or it may be energy failre or any other reasons. Imagine problem is determined. Signal transfer fails and it does not appear in the robot arm. It is so hard where the cable is broken or which cable is broken. A Programmable Logic Controller (PLC) nit is a very nice device for control applications. It offers a flexible strctre which enables the ser to enter his/her defined programs to rn in PLC. It takes few mintes to change the system parameters or the system itself. The operator does not deal with cables and connections too mch bt deals with program and its behaviors (reaction) to the system. Vl

8 Another advantage of PLC, it offers many featres (timers, conters, interrpts, arithmetic& logic operations etc.). The Operator can constrct very complex systems easily (compare to classical control system combined with electromagnetic switches). For example, a workman can break the concrete with a hammer in half hor or with a drill hammer within few mintes. PLC's are widely sed in indstrial places, factories, hotels, art galleries etc. where the physical vales sch as pressre, temperatre, hmidity, etc. are very important dring prodction process or for the environment conditions. In an art gallery, hmidity is a very important thing becase priceless paintings can be exhibited to the visitors and ths hmidity can destroy these paintings (hman effect on hmidity in the air) if the hmidity is not measred and controlled in short time intervals. A PLC makes the control of these physical parameters by sensing them with special sensors. The Project Consists of Three Chapters, Conclsion, Appendix and Reference. Chapter- I presents the description of PLC, the types of PLC and the se of PLCs Chapter-2 presents PLC strctre, PLC Commnication Protocols, PLC Programming and Programming Examples. Chapter-3 presents the hard-wired control systems with examples, indstrial control devices, commercial sensors and their applications inclding the other electronic devices and nits sed in conveyor carrying system prototype. vii

9 CHAPTER ONE PLCs and PLC TYPES 1.1 What is a PLC? A programmable logic controller, also called a PLC or programmable controller, is a compter-type (microprocessor based) electronic device which consists of integrated circits rather than electromechanical devices, performs control fnctions in an indstrial environment. PLCs inclde a programmable memory nit allocated to perform special fnctions sch as logical, arithmetical, timing, conting, and seqencing operations with internal and external commnication throgh digital or analog inpt/otpt modles to control indstrial machines or process. Conveyor systems, food processing machinery, textile machinery, pharmacetical prodcts machinery, ato assembly lines, PID control applications, physical qalities control (temperatre, pressre, hmidity, etc.) packaging and material handling are samples of PLC sage in today's world. Lights Pshbtton :3v, itches Figre 1.1 PLC application scheme 1

10 1.2 PLC History In the late 1960's PLCs were first introdced. The primary reason for designing sch a device was eliminating the large cost involved in replacing the complicated relay based machine control systems. Bedford Associates (Bedford, MA) proposed something called a Modlar Digital Controller (MODICON) to a major US car manfactrer. Other companies at the time proposed compter based schemes, one of which was based pon the PDP-8. The MODICON 084 broght the world's first PLC into commercial prodction. Early machines were controlled by mechanical means sing cams, gears, levers and other basic mechanical devices. Later, control system contained wired relay and switch control elements. These elements were wired as reqired to provide the control logic necessary for the particlar type of machine operation. This was acceptable for a machine that never needed to be changed or improved. When prodction reqirements changed so did the control system. This becomes very expensive when the change is freqent. Since relays are mechanical devices they also have a limited lifetime which reqired strict adhesion to maintenance schedles. Trobleshooting was also qite tedios when so many relays are involved. Machine control panels are sally inclded many, possibly hndreds or thosands of individal relays. The size cold be ot of concern bt complicated initial wiring of so many individal devices! These relays wold be individally wired together in a manner that wold yield the desired otcome. Were there problems? Who knows? These "new controllers" also had to be easily programmed by maintenance and plant engineers. The lifetime had to be long and programming changes easily performed. They also had to srvive the harsh indstrial environment. The soltion was to se a programming techniqe most people were already familiar with and replace mechanical parts with solid-state ones. In the mid70's, the dominant PLC technologies were seqencer state-machines and the bit-slice based CPU. The AMD 2901 and 2903 were qite poplar in Modicon and A-B PLCs. Conventional microprocessors lacked the power to qickly solve PLC logic in all bt the smallest PLCs. As conventional microprocessors evolved, larger and larger PLCs were being based pon them. 2

11 However, even today some are still based pon the 2903.(ref Allen Bradley's PLC-3) Modicon has yet to bild a faster PLC than their 984A/B/X which was based pon the Commnications abilities began to appear in approximately The first sch system was Modicon's Modbs. The PLC cold now talk to other PLCs and they cold be far away from the actal machine they were controlling. They cold also now be sed to send and receive varying voltages to allow them to enter the analog world. The 80's saw an attempt to standardize commnications with General Motor's manfactring atomation protocol (MAP). It was also a time for redcing the size of the PLC and making them software programmable throgh symbolic programming on personal compters instead of dedicated programming terminals or handheld programmers. Today the world's smallest PLC is abot the size of a single control relay! The 90's have seen a gradal redction in the introdction of new protocols, and the modernization of the physical layers of some of the more poplar protocols that srvived the 1980's. The latest standard (IEC ) has tried to merge PLC programming langages nder one international standard. We now have PLCs that are programmable in fnction block diagrams, instrction lists, etc. 1.3 Why Use PLCs The soft wiring advantage provided by programmable controllers is tremendos. In fact, it is one of the most important featres of PLCs. Soft wiring makes changes in the control system easy and cheap. If yo want a device in a PLC system to behave differently or to control a different process element, all yo have to do is change the control program. In a traditional system, making this type of change wold involve physically changing the wiring between the devices, a costly and time-consming endeavor. In addition to the programming flexibility we jst mentioned, PLCs offer other advantages over traditional control systems. These advantages inclde: Being solid state High reliability Simplicity of programming 3

12 Small space reqirements Very short response time Microprocessor based control Programmable memory Compting capabilities Commnication availability (PLC-PC with RS232 or RS485 or USB protocols) Modem PLCs can be controlled remotely by TCP/IP protocol throgh internet via special softwares. It is also possible to access PLC data throgh internet Software timers/conters Redces hardware/wiring cost and space reqirements and decreases the freqency of connection errors i.e., electrical arc, disconnection between devices Modlar I/0 interface Hman machine interface with optional visal control nit Easy maintenance, wiring and high MTBF(Mean Time Between Failres) Redced costs Ability to withstand harsh environments Expandability In a traditional system, all control devices are wired directly to each other In a PLC system, all control devices are wired to the PLC Figre 1.2 PLC and hard-wired systems comparison 1.4 Types of PLC PLCs can be classified into two grops according to their internal arrangement. Compact PLCs and Modlar PLCs. Below are given the necessary explanation for both PLC types. 4

13 1.4.a Compact PLCs Compact PLCs are manfactred as all the nits of PLC take place in the same casing. They generally have less memory and accommodate a small nmber of inpts and otpts in fixed configrations with less prices. They are ideal in small indstrial applications. There is also high capacity compact PLCs manfactred from different prodcers. 1.4.b Modlar PLCs In Modlar PLCs, the nits are separated (not on-board) and these nits are combined and connected to each other to form a single PLC system. They can have different memory capacity, I/0 nmbers, power spply p to the necessary limits. Below are given a modlar PLC and its featres manfactred by IDEC Inc. Figre 1.3 Idec FA3S Modlar PLC (IDEC Inc.) Idec F A3S Modlar PLC Key Featres: For CPUs available ms per basic instrction 1 to 8K program memory Spports p to 256 I/0 Bilt in ASCII commnications Interrpt and high speed I/0 Fiber optic remote I/0 Expansion RS232 commnication ports 5

14 Data link network with FA-NET RS485 Data acqisition Special modles are available for data commnication, fiber optic remote I/0, interrpt processing 1.5 PLC Configrations and Selection There are many kinds of PLCs with different featres and capacities from different manfactrers. Choosing correct type of PLC is vitally important for every programmer. Otherwise, it will waste the money nnecessarily and selected PLC model will not be sed in desired applications. The following criteria shold be considered for selecting a sitable and correct type of PLC: 1) Whether PLC will be sed in fixed or varios types of applications? a) Fixed applications - Compact PLC b) Expandable and varios applications - Modlar PLC 2) How many I/0 modles range is sitable for the applications? a) Up to 32 I/0 ports - Micro PLC b) Up to 128 I/0 ports - Small PLC c) Up to 1024 I/0 ports - Medim PLC d) Up to 4096 I/0 ports - Large PLC 3) What kind of inpt/otpt and PLC feed powers yo need in yor control system? For instance, 24VDC Power Spply/ 24VDC in/ 24VDC ot or 24VAC/24VAC/24VAC type or 240VAC/24VDC/ 24V Relay type etc. 4) Do yor applications need PID fnctions, thermocople otpt etc. in the PLC? 5) How mch memory is needed for PLC program and ser data? 6) Does yor PLC control system need special commnication configrations sch as DeviceNET, Profibs, Control Net and Ethernet Option Modles? 6

15 7) Does yor PLC system need Real Time Clock, high speed conters, mathematical fnctions( addition, sbtraction, mltiplication, division, sqare root, doble precision, floating point, cosine fnctions), hardware inpt interrpts etc. 1.5.a Micro PLCs Micro PLCs are designed and manfactred for the applications that need limited 1/0 nits and minimm PLC configrations. They are widely sed in conveyor systems, indstrial machines control, etc. Some micro PLCs have high speed conters bilt in casmg. Figre 1.4 DL-06 Micro PLC (Direct Logic Inc.) DL -06 Micro PLC Featres: 20 inpts I l 6 otpts 16-bit processor 14.8 Kbytes of total memory 229 instrctions, inclding 8 PID loops Expandable p to 100 1/0 PID capability, high-speed conting, floating point nmber handling Integrated high-speed inpts and plse otpt ASCII in/ot Thermocople inpt Bilt-in real-time clock/calendar Two commnication ports, inclding RS232/ 422/ 485 capability 7

16 Spports networking for MODBUS RTU master/slave, RTD temperatre inpt, a DeviceNET slave option modle, an Ethernet option modle, and a Profibs slave modle (NOTE]: Only one high-speed 1/0 featre may be in se at one time. Yo cannot se a high-speed inpt and the plse otpt at the same time.) 1.5.b Medim PLCs Medim PLCs have a few hndred I/0 nits where the application or control process needs high capacities and special commnication protocols. Medim PLCs are mainly sed in traffic light controls, traffic gidance systems, sewage treatment plants, climate controlled warehosing, transportation systems, mining indstry, chemical plants, material handling and packaging etc. Below are given Omron CH-Medim PLC key featres. Figre 1.5 Omron CJl Medim PLC (Omron Electronics) Omron CJl- M Series PLCs Featres: 120K words programming capacity p to 256K words data memory nanosecond exection time p to 2560 local 1/0, p to 3 racks CompoBs/S, RS-232C, 422/485, Ethernet, DeviceNet, ControllerLink, Profibs-DP, Protocol Macro. Rack-less design eliminates the need for a PLC rack, simplifying configration and lowering system costs Flash Memory Cards store p to 64 MB for easy program transfer and data storage 8

17 1.5.c Large PLCs Large PLCs are sed in complicated, hge control systems which needs data maniplation, data acqisition, reporting, etc. Large PLCs have extremely high capacities, special commnication protocols, PID modles, Math capabilities, extended data handling, fast speed processing etc. Large PLCs are typically sed in Plant Engineering applications sch as nclear plants, chemical plants, etc. Figre 1.6 ControlLogix Series PLC ControlLogix Series PLCs Featres: Mltiple processors 750K to SM bytes with non-volatile options available Up to 128,000 digital or 4,000 analog I/0 points with a wide range of digital, analog, and intelligent I/0 modles Local and remote I/0 Tag-based addressing It means yo no longer have to worry abot specific memory addresses. Logix atomatically creates the memory strctres reqired for stats and diagnostic information for instrctions and I/0 modles EtherNet/IP, ControlNet, DeviceNet, Universal Remote I/0, DFl I DH-485, DH+, RS-232 links, and other networks N etlinx open network It helps to save system design and programming time and needs less hardware becase gateway controllers are not needed 9

18 Integrated motion control It eliminates the need to create special programming to commnicate, coordinate, and synchronize motion and seqential control among mltiple axes of motion.) Drm timers and seqencers Timers/conters/shift registers Sbrotines and interrpts Machine diagnostics Enhanced data handling ( compare, data conversion, move register/file, matrix fnctions, block transfer, binary table, ASCII table, LIFO, FIFO) Math operations (Addition, sbtraction, mltiplication, division, sqare root, doble precision, floating point, cosine fnctions) ViewAnyWare visalization prodcts 10

19 CHAPTER TWO PLC INTERNAL STRUCTURE & PROGRAMMING TECHNIQUES 2.1 How a PLC Operates? A programmable controller operates by checking its inpts and rnning the program according to the states of inpts and reslts of the otpt continosly. Programmable controller performs this operation sing basic sections: The central processing nit The inpt/otpt interface system Memory Power spply nit Commnication Unit Screw terminals for inpt I ines ~ ~ r g I 11 Inpt Interface s I ~I I I L C - Power Spply Com m nication Line for Extension -t-,-j Screw tertrlw;l i for otpt I ines CPU Otpt Interface I I I I I Figre 2.1 PLC Internal Strctre Block Diagram 11

20 2.2 Central Processing Unit Central Processing Unit (CPU) is the brain of a PLC controller. CPU itself can be either a microcontroller or a microprocessor. Early PLCs were 8-bit microcontrollers sch as 8051, and now these are 16- and 32-bit microcontrollers. There are two fndamental CPU architectres: The Harvard architectre and Von Nemann architectre. (li) Progtam memory (b) Addres,s bs (program) Program memory Address bs CPU Data bs CPU Data bs (program) Address bs (data} Data me.mory, pertphera.ls Data bs (data) Data memory, peripherals Figre 2.2 (a) The von Nemann strctre; (b) the Harvard strctre. In the conventional von Nemann architectre, program and data memory share the same address and data bses, and are hence both within the same memory map. This is illstrated in very simple form in Fig. 2.2(a). This approach is simple, robst and practical, and has been widely and sccessflly applied. If data memory is being accessed, program memory lies idle, and vice versa. It is, however, possible to have more than one address and data bs, and hence to place data and program memory in different memory maps. This approach, sometimes called a Harvard strctre, is shown " in simple form in Fig 2.2(b ). Instrctions can now be fetched independently from, and if necessary simltaneosly with instrction exection, thereby eliminating the von Nemann bottleneck. The two data bses can now be of different sizes, as can the two address bses. This allows each to be optimized for its own se, and has important implications in certain processor strctres. PLC is basically a microcontroller system (in von Nemann strctre) with peripherals that can be digital inpts, digital otpts or relays as in or case. However, this is not an 12

21 "ordinary" microcontroller system. Large teams have worked on it, and a checkp of its fnction has been performed in real world nder all possible circmstances. CPU takes care of commnication, interconnectedness among other parts of PLC controller, program exection, memory operation, overseeing inpt and setting p of an otpt. PLC controllers have complex rotines for memory checkp in order to ensre that PLC memory was not damaged (memory checkp is done for safety reasons). In general, CPU nit makes a great nmber of check-ps of the PLC controller itself so evental errors wold be discovered early. Yo can simply look at any PLC controller and see that there are several indicators in the form of light diodes for error signalization. Software of CPU is entirely different from assemblers sed ths far, sch as BASIC or C. This specialized software is called "ladder" (name came abot by an association of program's configration which resembles a ladder, and from the way program is written ot). I N p T s r : Processor Power Spply Memory I I I I 0 T p T s ~ CPU I I Figre 2.3 CPU Strctre Block Diagram The Inpt Interface System Intelligence of an atomated system depends largely on the ability of a PLC controller to read signals from different types of sensors and inpt devices. Keys, keyboards and by fnctional switches are a basis for man verss machine relationship. On the other hand, in order to detect a working piece, view a mechanism in motion, check pressre or flid level yo need specific atomatic devices sch as proximity sensors, marginal 13

22 switches, photoelectric sensors, level sensors, etc. Ths, inpt signals can be logical ( on/off) or analoge. Smaller PLC controllers sally have only digital inpt lines while larger also accept analoge inpts throgh special nits attached to PLC controller. One of the most freqent analoge signals are a crrent signal of 4 to 20 ma and millivolt voltage signal generated by varios sensors. Sensors are sally sed as inpts for PLCs. Yo can obtain sensors for different prposes. They can sense presence of some parts, measre temperatre, pressre, or some other physical dimension, etc. ( ex. Indctive sensors can register metal objects). Other devices also can serve as inpts to PLC controller. Intelligent devices sch as robots, video systems, etc. often are capable of sending signals to PLC controller inpt modles (robot, for instance, can send a signal to PLC controller inpt as information when it has finished moving an object from one place to the other.) a The Inpt Interface Configration The inpt interface is placed between inpt lines and a CPU nit. This nit is also called as "inpt adjstable interface". The prpose of adjstable interface is to protect a CPU from disproportionate signals from an otside world. Inpt adjstment modle trns a level of real logic to a level that sits CPU nit ( ex. inpt from a sensor which works on 24 VDC mst be converted to a signal of 5 VDC in order for a CPU to be able to process it). This is typically done throgh opto-isolation, and this fnction is given by the figre shown below. Inpt adjstable int erfe ce Inpt.i., //. /,' LED I / '.s;z'w~~ ~ 1,.,.,. - '\ ~- t;-" P r1 c,1 o tr <1 n :; rst or CPU Figre 2.4 The inpt and the CPU interface Opto-isolation means that there is no electrical connection between external world and CPU nit. They are "optically" separated, or in other words, signal is transmitted 14

23 throgh light. The way this works is simple. External device brings a signal which trns LED on, whose light in tm incites photo transistor which in tm starts condcting, and a CPU sees this as logic zero (spply between collector and transmitter falls nder 1 V). When inpt signal stops LED diode trns off, transistor stops condcting, collector voltage increases, and CPU receives logic 1 as information The Otpt Interface System Atomated system is incomplete if it is not connected with some otpt devices. Some of the most freqently sed devices are motors, solenoids, relays, indicators, sond signalization and similar. By starting a motor, or a relay, PLC can manage or control a simple system sch as system for sorting prodcts all the way p to complex systems sch as service system for positioning head of CNC machine. Otpt can be of analoge or digital type. Digital otpt signal works as a switch; it connects and disconnects line. Analoge otpt is sed to generate the analoge signal ( ex. motor whose speed is controlled by a voltage that corresponds to a desired speed) a The Otpt Interface Configration Otpt interface is similar to inpt interface. CPU brings a signal to LED diode and trns it on. Light incites a photo transistor which begins to condct electricity, and ths the voltage between collector and emitter falls to 0.7V, and a device attached to this otpt sees this as a logic zero. Inversely it means that a signal at the otpt exists and is interpreted as logic one. Photo transistor is not directly connected to a PLC controller otpt. Between photo transistor and an otpt sally there is a relay or a stronger transistor capable of interrpting stronger signals. Otpt adjstable interface CF'U O! LED /// \,., \ \ Photo transistor Figre 2.5 The otpt and the CPU interface 15

24 2.2.3 Memory System memory (today mostly implemented in FLASH technology) is sed by a PLC for a process control system. Aside from this operating system it also contains a ser program translated from a ladder diagram to a binary form. FLASH memory contents can be changed only in case where ser program is being changed. PLC controllers were sed earlier EPROM memory instead of FLASH memory which had to be erased with UV light (chip shold be exposed to UV light abot 10 mintes) and programmed on programmers. With the se of FLASH technology this process was greatly shortened. Reprogramming a program memory is done throgh a serial cable in a program for application development. User memory is divided into blocks having special fnctions. Some parts of a memory are sed for storing inpt and otpt stats. The real stats of an inpt is stored either as "1" or as "O" in a specific memory bit. Each inpt or otpt has one corresponding bit in memory. Other parts of memory are sed to store variable contents for variables sed in ser program. For example, timer vale, or conter vale wold be stored in this part of the memory Power Spply Electrical spply is sed in bringing electrical energy to central processing nit. Most PLC controllers work either at 24 VDC or 220 V AC. On some PLC controllers yo'll find electrical spply as a separate modle. Those are sally bigger PLC controllers, while small and medim series already contain the spply modle. User has to determine how mch crrent to take from I/0 modle to ensre that electrical spply provides appropriate amont of crrent. Different types of modles se different amonts of electrical crrent. This electrical spply is sally not sed to start external inpts or otpts. User has to provide separate spplies in starting PLC controller inpts or otpts becase then yo can ensre so called "pre" spply for the PLC controller. Pre spply for the PLC means that indstrial environment can not affect it damagingly. Some of the smaller PLC controllers spply their inpts with voltage from a small spply sorce already incorporated into a PLC. The desired property of a good power spply is that, being able to reglate the voltage within predefined limits and spplying reqired crrent amont for the nits. So that, the CPU and the other electronic devices will not be affected de to voltage changes and the reqired power will be provided. 16

25 2.3 Commnication in PLCs PLCs have two types of commnications. (1) internal commnication (2) external commnication Internal Commnication Since PLCs are microprocessor based systems, they need external integrated circits to control and commnicate between CPU, RAM, memory and other peripherals. These commnications are provided by three basic bses: Data Bs, Control Bs and Address Bs. Microprocessor I Data Bs fl I L L I A dress Bs I I Control Bs,,,, t,,,, t ',,, t,, 11' Non- Read- I Interface I I Interface I Volatile Memory Write Memory I External Device External Device Figre 2.6 CPU and other peripherals commnication a Data Bs The data bs is sed for transferring data between microprocessor and external devices sch as memory. Most embedded microprocessors have either an 8-bit or 16-bit data bs. The data bs is a bi-directional and data can flow either from microprocessor to devices or devices to microprocessor. Devices which can be ready by the processor mst have tri-state logic connecting to the data bs to avoid contention b Address Bs The address bs is sed to specify the device, and the location within the device, that is being accessed. Most embedded microprocessors have either an 16-bit, 24-bit or 32-bit address bs. The address bs is nidirectional and is controlled by the microprocessor. All the devices mst monitor the address bs, and only respond when the address assigned to them appears on the bs. 17

26 2.3.1.c Control Bs A typical control bs might have the following lines: RESET: (active-low) pts the processor and devices in a well-defined initial state on power-p R/W: read not write - defines the direction of data flow DAV: (active low) data valid- data on the data-bs is valid DTA: (active low) data transfer acknowledge - data transfer is complete IRQ: (active low) interrpt reqest External Commnication PLC programmers or sers need an external commnication to access to PLC via personal compters (PCs). RS232, and RS482 protocols are sed in this manner. In some complicated applications, PLC interface with sensors, transdcers, switches, etc. is very boring, not easy to handle with connections. Today's software engineers, programmers, commnication engineers have been developing new software programs, commnication protocols for this prpose. For example, DeviceNET is a commnication protocol for PLC-indstrial devices interface with a smart soltion in a flexible strctre. Below are given the most important commnication protocols sed in PLCs a The RS-232 Protocol The RS-232-C is designed to carry ot point-to-point commnications between two devices, a Data Terminal Eqipment (DTE) and a Data Commnication Eqipment (DCE). The DTE is normally a compter and the DCE, a peripheral, which can be any kind of digital instrment. The standard defines electrical, mechanical, and fnctional characteristics. The electrical characteristics inclde parameters sch as voltage levels and cable impedance. The mechanical section describes the nmber of pins of the connectors and the fnction assigned to each pin. Althogh the connector itself is not specified, in practice DB-25 or DB-9 connectors are almost always sed. The fnctional description defines the fnctions of the different electrical signals to be sed. 18

27 Two important limitations of RS-232-C are the low transfer rates (p to 20 kilobits per second) and the maximm length of the wires (arond 16 meters). To overcome these limitations, the new standards, RS449 (mechanical) and RS423 ( electrical), have been defined. These new standards are pward-compatible with RS-232-C and can operate at data rates p to 10 megabits per second and at distances of p to 1200 meters. However, changing to a new standard is a long and costly process, so the penetration of this new standard in the market is, as yet, very limited. Despite its limitations, RS-232-C commnications are widely sed, specially in low-cost installations. However, if more sophisticated commnications are reqired, more specialized bses, sch as the GPIB or field bses mst be sed b Fieldbses Fieldbses are designed to commnicate digital devices and instrmentation systems in indstrial environments. Sensors, actators, freqency converters (to control electrical motors), position controllers, PLC's and indstrial compters are examples of the wide variety of devices which can be fond in an indstrial plant and which mst commnicate with each other. A fieldbs is an interconnection system which allows the commnication of all these types of devices sing a defined commnication protocol. To connect a device to a determined fieldbs, the device mst be specifically developed for that particlar fieldbs. Fieldbses provide important advantages in relation to traditional indstrial commnications. Analysis of actal fieldbs projects show significant savings when they are sed instead of conventional cabling arrangements and this is tre even for small installations. Costs are also redced in plant design, installations, and operations. Dring the project design stage, flly integrated ser-friendly project design tools allow field devices to be integrated qickly and easily. As a reslt of this centralized engineering, the nmber of potential sorces of error is sbstantially redced. In the installation and cabling of the field devices the cost advantage is particlarly clear. Instead of thick bndles of cables, jst one two-wire bs cable is laid. In addition to saving time and material, a frther benefit is that the likelihood of wiring errors is drastically redced. 19

28 In operations, the benefits of fieldbs soltions are shown primarily in trobleshooting and maintenance. Errors can be more easily detected, analyzed and localized, and the stocking of spares is simplified. When sbseqent plant pgrades arise, the field bs is the better choice, too. Instead of complex recabling, or tilization of expensive cable reserves, the existing bs is simply extended to the new field devices. Dring 1990s a significant nmber of field bs definitions were achieved. However, each bs definition presents particlar characteristics and, conseqently, some bses are more sitable for determined installations than others. For example, the AS-I bs (1993) is oriented to low-level commnications, connecting the sensors and actators of a plant with its atomation system. Other bses, sch as PROFIBUS (1994/1995), are devoted to managing higher level commnications, which allows commnication among PLC's, drive nits, 1/0 modles and indstrial compters. A pecliar type of field bs is the CAN bs (1995), which was specifically developed for the atomotive indstry. The CAN bs is sed to commnicate and control the great nmber of digital devices which can be fond in a vehicle: ABS breaks, airbags, electric windows, etc. Other important examples of field bses in the market are INTERBUS-S (1984), DeviceNet (1994) and the Fondation Fieldbs Hl (1995). Major international efforts for the standardization of Fieldbs can be sbdivided into two categories: the first one is based on the se of the Data Link Layer (DLL) of a centralized control protocol sch as FIP Fieldbs, and the second one is based on the distribted control protocol. Figre 2. 7 Common Fieldbs Protocol Layers 20

29 2.4 PLC Operation Principle A PLC works by continally scanning a program. We can think of this scan cycle as consisting of three important steps. There are typically more than three steps bt we can focs on the important parts simply. Typically the others are checking the system and pdating the crrent internal conter and timer vales. CHECK INPUT STATUS EXECUTE PROGRAM UPDATE OUTPUT STATUS Figre 2.8 Illstration of a scan process Step 1) CHECK INPUT STATUS -First the PLC reads (checks) each inpt device sch as sensors, transdcers, limit switches, psh bttons, etc. to determine if it is on or off. In other words, is the sensor connected to the first inpt on? How abot the second inpt? How abot the third... It records the state of each inpt into its memory location to be sed in the following step. Step 2) EXECUTE PROGRAM -Next the CPU exectes the program, starting with the first instrction and proceeding to the end instrction. Maybe yor program said that if the first inpt was on then it shold trn on the first otpt. Since it already knows which inpts are on/off from the previos step it will be able to decide whether the first otpt shold be trned on based on the state of the first inpt. It will store the exection reslts for se later dring the next step. The immediate I/0 instrctions give yo immediate access to inpts and otpts dring the exection of either the program or an interrpt rotine. If yo se interrpts in yor program, the interrpt rotines that are associated with the interrpt events are stored as part of the program. The interrpt rotines are not exected as part of the normal scan cycle, bt are exected when the interrpt event occrs (which may be at any point in the scan cycle). 21

30 Step 3) UPDATE OUTPUT STATUS -Finally the PLC pdates the stats of the otpts. It pdates the otpts based on which inpts were on dring the first step and the reslts of execting yor program dring the second step. Based on the example in step 2 it wold now trn on the first otpt becase the first inpt was on and yor program said to trn on the first otpt when this condition is tre. After the third step the PLC goes back to step one and repeats the steps continosly. The time that a PLC spends dring the scan process is called "scan time". In a scan time period, PLC checks each inpt and store the state of these inpts, pdates its inpts and reslts otpt as activation or deactivation of related otpt. Scan time depends on two parameters: (1) the amont of memory taken by the control program and (2) the type of instrctions sed in the program (which affects the time needed to execte the instrctions). The time reqired to make a single scan can vary from a few hndred nanoseconds to 50 milliseconds. 2.5 PLC Programming Langages There are a lot of PLC manfactrer companies. For this reason, PLCs are programmed in different langages. Ladder, Boolean and transition fnction chart are main langages. Transition fnction chart originated in France. It is known as "Grafcet". This langage is not common, so that it will not be explained. Ladder program was developed for technicians who are already familiar to classical electrical control systems. Some PLC manfactrers offer Boolean langage to program their PLCs. Boolean langage is similar to assembly programs. Instrctions are the abbreviations of the fnctions. Modern PLCs can be programmed in high- level langages sch as C, C++, etc. Below are given the necessary explanation for each programming langage. 2.5.a Ladder Langage PLCs were manfactred as an alternative to the classical electrical control systems. Since the sers of PLCs are mostly electricians, technicians and engineers, the langage of PLC shold be familiar to them. The ladder langage is the most sitable PLC langage for these people becase the ladder langage is very similar to relay based control systems. Ladder langage is composed of symbols with addresses, destinations and other parameters according to the instrction. 22

31 Below are given a hard-wired representation. control circit and its eqivalent PLC ladder LI CLASSICAL CONTROL SYSTEM MP PLC LADDER PROGRAM START STOP..L ISi~ I I ~ I I ~ 13 ONDElAY AL TR A2 (A) (B) ISII' ~1,, M ( I '\ l~{ ' ) I ~SI T37 IN 300 PT TAR~S) TON R / I ( ) Xl X2 I. END -( ) I M RUN PL ( ) Figre 2.9 Classical Control Circit and Its PLC Ladder Program In the above given circit, it is clearly shown that the motor will start after 30 seconds if the start btton is pressed. Actally, in the figre it is not mentioned when the motor will start exactly. The electrician or technician has to select correct type of timer relay for desired time interval and adjst it to 30 second position. As yo see, when the operator press the start btton and release it, the contactor will be de-energized and timer will stop operating. To prevent this event, start contact is connected to N/0 contact of contactor in parallel. This is called as "locking process" in electrical control systems. This will be explained in details later. In the same figre, its eqivalent PLC representation is shown. Yo can see how PLCs are flexible compare to classical control systems. Let s change the dration for the motor start and make it 30 mintes. Is it possible to se same timer for this time interval? Certainly it is not. Timers are made in fixed time intervals bt there are also timers can be programmed daily, weekly or monthly sch timers are called as "switch compters ". These switch compters are very expensive, a few hndred dollars. 23

32 2.5.b Boolean Langage Some PLC manfactrers spport Boolean langage in their PLC softwares. PLC software program converts the program into a sitable form that PLC CPU nderstands, process it. This conversion is called as "program assembly". Before the program is sent ( downloaded) to the PLC, the software assembles it into the hexadecimal form and sends these information as digital signals throgh the commnication ports (RS232, RS485 or USB) of a PC. Programming langage is jst an interface between assembler and the programmer. Boolean langage is commonly sed by compter engineers, software engineers who are related with atomation in large plant engineering applications. Boolean langage ses short abbreviations of logical operands for PLC commands. These logical commands are AND, OR, NOT, NAND, NOR, etc. Their fnctions are the same as logical gates se in digital electronics. In addition to these commands, there are some commands which are similar to microprocessor commands sch as interrpt, LIFO, FIFO, and move, rotate, shift commands. Below are given some Boolean commands for different PLCs from different manfactrers. Table 2.1 Boolean langage commands from different PLC manfactrers Loqical Expression S5-90U S7-200 OMRON HITACHI MITSUBISHI AND A A AND AND AND OR 0 0 OR OR OR NOT N NOT NOT NOT I AND NANO AN AN NOT ANI AWi NOR ON ON OR NOT ORI OR I AND BLOCK A( A LO AN LO AN B AN B OR BLOCK 0( 0 LO OR LO ORB ORB LOAD - LO LO LO LO INPUT I LOAD COMPLEMENT - LON LO NOT LO I LO I OUTPUT Q Q OUT OUT OUT DESIGNATE TO OUTPUT = = OUT OUT OUT END OF PROGRAM BE MEND END END END 24

33 FESTO Ladder Program BFD I Boolean Program BF1.. Bf2 SF3 LD FLAG o:...i i ii I I C ) AND NOT FLAO 1 AND FlAG 2 SJ:'3 Sf4 SF$ =,1 111 C l =FLAG 3 LD NOT FLAG 3 AND NOT FLAG 4 =FLAG 5 LD PROO 0 IDEC AEG MITSUBISHI 2 $,~1H H ): ~illi 400 ihth l E! rn ElO ;11,15 H I I I I--< } EJ H ime 1H1H J LOD 1 MiDNOT 2.AND 3 OUT 200 LODNOT 210.ANDNOT 405 OUT 400 END UN UN UN PE El E24 E10 Alo E3 E4.M128 xm :<4rn X4~7 Yn1 H1i!H) LD :X413 "'M\TI 10-.AND X407 K40$ X4Q6 M1DQ ih1h) OUT Y431 X4Uo MU 1{405 OUT MlOO Figre 2.10 Ladder and Boolean langage programs from varios PLC manfactrers

34 2.6 Introdction to PLC Programming In this section, Siemens S7-200 PLCs will be introdced and the ladder langage will be sed for PLC programming Siemens S7-200 PLCs The S7-200 Micro PLC is the smallest, compact type programmable controller in SIMATIC S7 family. The central processing nit is inside the PLC nit. Inpt/Otpt nits are placed on the main nit and these nits are not separable from the PLC. Inpts take the analog/digital information signals from field devices, sch as switches, sensors, transdcers, etc. and introdce them to the PLC. Otpts actate ( control) other devices, sch as motors, pmps, solenoids, etc. The programming port is the connection between PLC and PC. PLC programs are sent to the device via this commnication port. ( p z==:::s. Ofhi1~ Mr.itt:rs PLC Port Inpts Figre 2.11 Siemens S7-200 Micro PLC The S7-200 family members are classified according to their CPU types. There are for S7-200 CPU types: S7-221, S7-222, S7-224, S7-226, and S7-226XM and three power spply configrations for each type. The model description indicates the type of CPU, the power spply, the type of inpt, and the type of otpt (Figre 2.12). 26

35 ~II 221 DC/DC/DC 221 AC/DC/Relay 22.2 DC/DC/DC 222 AC/DC/Relay 224 DCIDC}DC 224 AC/DC/Relay Table 2.2 The S7-200 CPU Types and Descriptions 20. 4,-:28.8 VDC VAC Hz VDC 85-2&1 VAC 47-' 33 Hz 20.4,-:28.S VDC VAC Hz f3 DC tnpts 14 DC Otpts a DC Inpts 4 Relay Otpts 8 DC Inpts 16 DC Otpts 8 DC Inpts 6 Re1ay Otp1s 14 DC Inpts 110 DC Otpts 14 DC t:npts 10 Relay Otpts Inpt ,Otp1:.rt Figre 2.12 S7-200 CPU Description a Mode Switch and Analog Adjstment The mode switch is a toggle switch that can be adjsted to three positions. RUN, STOP and TERM positions. When the mode switch is in RUN position, the CPU starts to rn the program loaded to the PLC and exectes this program. According to the states of inpts, the otpts can vary in time. When the mode switch is in the STOP position the CPU is stopped. When downloading/ploading a program into the PLC, the PLC shold be in this position. In the TERM position, the programming device can select the operating mode. The analog adjstment is sed to increase or decrease vales stored in special memory. These vales can be sed to pdate the vale of a timer or conter, or can be sed to set limits. CJ CJ [J.i,l,I,1 CJ CJ [J 27

36 2.6.1.b Inpts Figre 2.13 Mode Switch and Analog Adjstment Inpt devices can be pshbttons, switches, limit switches, proximity switches, photoelectric sensors and other sensing devices. These devices are connected to the terminal strip nder the bottom cover of the PLC (See Figre 2.14 )... mlp. dij UltrasonicTrahsdcer Proximity switch. Pshbtton Switch ~..Inp1.,1t Devices ronnectedhere Figre 2.14 Siemens S7-200 Inpts c Otpts Typical otpt devices are signal lamps, contactors, relays, solenoids, otpt transdcers, etc. These devices are connected to the terminal strip nder the top cover of the PLC. It is not necessary to connect them to the PLC when testing a program to see the effects of the program. The LED is lit for related otpt if that otpt is active. Otpt Devices Wired Here / sortsterter Motor Starter (Actator) 28

37 Figre 2.15 Siemens S7-200 Otpts Timers Timers are devices that cont increments of time. Yo can se timers to implement time-based conting fnctions. Timers are sed in traffic lamps, conveyors, chemical process applications where the time is essential for the applications. The S7-200 provides two different timer instrctions: the On-Delay Timer (TON), and the Retentive On-Delay Timer (TONR). Both TON and TONR timers time p while the enabling inpt is on. The timers do not time p while the enabling inpt is off, bt when the enabling inpt is off, a TON timer is reset atomatically and a TONR timer is not reset and holds its last vale. Therefore, the TON timer is best sed when yo are timing a single interval. The TONR timer is appropriate when yo need to accmlate a nmber of timed intervals. S7-200 timers have the following characteristics: Timers are controlled with a single enabling inpt, and have a crrent vale that maintains the elapsed time since the timer was enabled. The timers also have a preset time vale (PT) that is compared to the crrent vale each time the crrent vale is pdated and when the timer instrction is exected. A timer bit is set or reset based pon the reslt of the comparison of crrent vale to the preset time vale. When the crrent vale is greater than or eqal to the preset time vale, the timer bit (T-bit), is trned on. When yo reset a timer, its crrent vale is set to zero and its T-bit is trned off. Yo can reset any timer by sing the Reset instrction, bt sing a Reset instrction is the only method for resetting a TONR timer. Writing a zero to a timer's crrent vale does not reset its timer bit. In the same way, writing a zero to the timer's T-bit does not reset its crrent vale. IN IN TONR PT :n 29

38 2.6.2.a On-Delay Timer (TON) ~\..~"'-.~~ '\.~~ ~')~~~ ~\. ~\..~~"-~ On-Delay Timer (TON) starts to time p when its inpt is activated. It contines timing p if its inpt is still on. If the inpt is de-activated at any time dring the operation, the timer is reset and it will stop timing p. When the preset time vale is reached the related contact of the timer is activated. Figre 2.17 On-Delay Timer Example 1) A motor is controlled by PLC and the control system performs the following fnction: Motorl operates for 30 seconds and stops after start btton is pressed. The operator can stop the motor by pressing the stop btton. SOLUTION: Correct bt non-trexlblejnot easv.to nderstand BETTER,$Jar\ :Sfap t3'! Motoi1 ~11 l1i < iv,;11,~ symbolic A dressing ) Network 2 QO.O T87 IN TON 10,1 Network iPT l Net.work.2 Tmi(,b Coilih,l,ofMiloF :\. symbolic """ m \..... Information lin ron I. T able END) 300iPT f Network Explanation When start btton is pressed, "Start" contact becomes on (logic 1 ). "Stop" and "T37" normally closed contacts are on if the stop btton is not pressed and T37 timer is not active. Ths, "Motorl" otpt coil becomes active (logic 1 ). When start btton is released, "Start" contact becomes off and "Motorl" otpt coil becomes off 30

39 respectively. If we pt "Motorl" contact parallel to "Start" contact, the motor will not stop after we release start btton. This process is called as "locking process". T37 timer starts to time p becase its inpt (Motorl contact) is enabled. When preset time is reached, its Normally Closed (N/C) contact opens the contact and motor stops b Retentive On-Delay (TONR) The Retentive On-Delay Timer (TONR) operation principle is similar to TON type timer. It starts to time p when its inpt is activated. The difference is that it does not reset when its inpt is de-activated. The only way to stop the timer is to se a reset instrction. Preset time vale is selected according to the table (Table 2.3). For instance, for 30 seconds time dration, T37 can be written with preset vale = IN Figre 2.18 Retentive On-Delay (TONR) Timer Table 2.3 Timer Nmbers and Resoltions 31

40 "TIC)~Ty +'..1l f.'' J'~!'.,1)'1'A'7..A.of\ "'i-:'j Y't~G~,t$1,f:v T\:!~ T{),P c122;,s4i,;0 10:ms:. 32,7;~ a T3~ to.'!'36, TQ,7 :totij}ct,. '.. >. <<fc,}y::'.:-_:-. {;.:.CC".{ '') mn;r; I i 111st Hims ntr&tto.3. m1d1.,ofri21 ttf f~~i;ts, ~tfottiji, Tttil to T21K5; ts: fo T~!il T69tol'S75t.:,":.'.//:::.-,~;>~,._,... :,.,.."~ -:. "><: tjsihotf1itn$' Jtrn~,r: o.~.o.. 1;3:z ::11.. IJN: TON PT T32 Q0,0.,,..,,); i------<e},j[:)) s,ritt a:10-ms,.1jme'.r fa3,!on sioo' :a?1fr~::m:snnf!it ~~t '.>. li~i~;, mi t'.;lil,o: I {! f ek)d) Conters Conters are sed in the same manner as electronic conters. Electronic conters cont p or down when the clock plse is sent each time. Conting mechanism is a fnction of central processing nit. There are two types of conters. Normal conters and high speed conters. Normal conters are the p conter (CTU), the down conter (CTD) and the p/down conter (CTUD). The S7-200 conters have the following characteristics: The Up Conter (CTU) conts p from the crrent vale of that conter each time the cont-p inpt makes the transition from off to on. The conter is reset when the reset inpt trns on, or when the Reset instrction is exected. The conter stops pon reaching the maximm vale (32,767). The Up/Down Conter (CTUD) conts p each time the cont-p inpt makes die transition from off to on, and conts down each time the cont-down inpt makes the transition from off to on. The conter is reset when the reset inpt trns on, or when the Reset instrction is exected. Upon reaching maximm 32

41 vale (32,767), the next rising edge at the cont-p inpt cases the crrent cont to wrap arond to the minimm vale (-32,768). Likewise on reaching the minimm vale (-32,768), the next rising edge at the cont-down inpt cases the crrent cont to wrap arond to the maximm vale (32,767). When yo reset a conter sing the Reset instrction, both the conter bit and the conter crrent vale are reset. The Up and Up/Down conters have a crrent vale that maintains the crrent cont. They also have a preset vale (PV) that is compared to the crrent vale whenever the conter instrction is exected. When the crrent vale is greater than or eqal to the preset vale, the conter bit (C-bit) trns on. Otherwise, the C-bit trns off a Up Conter The p conter conts p from a crrent vale to a preset vale (PV). Inpt of the conter (CU) checks each transition from off to on that comes from inpt contacts. Each transition from logic O to logic 1 increases one to the previos vale and when the crrent vale is eqal to or greater than the preset vale, the related contact of the conter is activated (logic 1 ). c cm ( Figre 2.19 The Up Conter Example 2) In a packaging machine, retroreflective photoelectric sensor checks the nmber of bottles. The worker starts the conveyor by pressing the start btton and stops it with 33

42 stop btton. Each package contains 6 bottles and when six bottles pass throgh the sensor to fall onto the adjacent belt for bottling, the belt pases for 5 seconds and resmes carrying the belt contents. This process contines ntil the conveyor is stopped. Figre 2.20 Bottling Machine Example SOLUTION: T37. Nehvork.2 Sensor1 CLI' COi CTI~ Motor1 CO T37" IN TON +50 -j PT I SYMBOL TABLE: View I Symbol Table in MicroWIN 3.2 Siemens PLC Software Prog. Name Address Comment Start 10.0 Start Btton is connected to 10.0 stoo 10.1 Stoo Btton is connected to

43 Sensor Photoelectric Sensor is connected to 10.2 Motor1 QO.O Motor is actated by sing a contactor or a relay whose energitizing A 1-A2 contact is connected to QO.O and N terminals When start btton is pressed and released "Start" contact becomes on and it locks the otpt coil with its parallel contact(motorl ). When sensor senses the bottle "Sensorl" contact is on (logic 1) and adds one to the conter. When six bottles pass throgh the sensing area of sensor, the conter crrent vale reaches to 6 and N/C contact of CO in the first rng changes to off state. Ths, when 6 bottles passed, the motor stops for a while. In Network3, N/0 contact of CO starts the timer T37. After 5 seconds from the motor stop time, the T37 timer is activated becase 5 seconds elapsed. The N/0 contact of T37 timer in the first network is now on and it starts the motor again. When stop btton is pressed the otpt contact parallel with "Start" contact becomes off and it breaks ot the locking process b Up/Down Conter(CTUD) The p/down conter conts p or down from the preset vale each time either CD or CU transitions from off to on state. When the crrent vale is eqal to the preset vale, the otpt QU trns on. When the crrent vale (CV) is eqal to zero, the otpt QD trns on. The conter loads the crrent vale (CV) with the preset vale (PV) when the load inpt (LD) is enabled. Similarly, the conter resets and loads the crrent vale (CV) with zero when the reset (R) is enabled. The conter stops conting when it reaches preset or zero. CD c R LD P\l XXX CllJD Figre 2.21 Up-Down Conter Compare Instrctions 35

44 Compare commands are sed to compare two parameters either two bytes, integer nmbers or real nmbers. Compare instrctions are very sefl specially when seqential actions take place in a control system. For example, a control system performs the following fnction the motor starts for 30 seconds and stops. Then, mixer starts operation for 50 seconds and stops. After that, heater operates for 20 seconds and stops. It is not a good programming method to se a separate timer for each device becase timers are limited and too many timers make the program blky and complicated a Compare Byte The Compare Byte instrction is sed to compare two vales: nl to n2. A comparison of nl = n2, nl >= n2, or nl <= n2 can be made. The contact is on when the comparison is tre. Operands: nl, n2: VB, IB, QB, MB, SMB, AC, Constant b Compare Word Integer The Compare Word Integer instrction is sed to compare two vales: nl to n2. A comparison of nl = n2, nl >= n2, or nl <= n2 can be made. The contact is on when the comparison is tre." Operands: nl, n2: VW, T, C, IW, QW, MW, SMW, AC AIW, Constant, *VD, *AC, SW Example S) A control system performs the following process. When start btton is pressed, the crane starts operation to carry the blocks of planks from floor onto the belt and stops. It takes 30 seconds for this operation. Then, Motorl starts to carry the belt contents and it also stops 60 seconds later. Ctting tool starts to ct planks and it stops after 20 seconds and all machines will be off at the end of 110 seconds. SOLUTION 36

45 Net to'r k.t.start T37. Crane.. J. :r <....=1 I '. crane f ) Networ~ '2 r3.1 Crane IN TON Motor1 t300ipt I T37 T37 Motor l >=I I I «=1 l.( ; +90Q N;rl:work4 T37 T31) C tti,ng =II l~=1j c. J +90, Net totui ''END) The control system is started with start btton. When start btton is pressed, "Start" contact becomes on and "T37 <= I 300 " contact becomes on becase the contact satisfies the condition. This comparison contact is on when the crrent vale of the timer T37 is less than or eqal to 300. Now, crane is on and the T37 timer starts timing p. After 30 seconds, crane stops de to "T37 <= I 300 "contact in Networkl, which will be off depending on the contact condition(<= 30 seconds). The T37 timer contines timing p even its inpt contact "Crane" contact is off bt "Motor!" contact does not let the timer to stop, being activated ( on) before the crane is off. In Network3, "T37 >= I 300 "and "T37 <= I 900 "contacts activate "Motor!" otpt coil together. If "T37 >= I 300 " contact were placed alone the motor wold not stop and 60 seconds operation restriction wold not be carried ot. 37

46 In Network4, ctting tool operation takes place after 90 seconds from crane start time. We declare this by T3 7 >= I 900 " contact and "T3 7 <= I 1100 " contact which will stop ctting tool. 38

47 CHAPTER THREE INDUSTRIAL APPLICATIONS & CONVEYOR CONTROL SYSTEMS 3.1 Introdction to Control Systems Electrical control systems are designed sing basic devices or eqipments sch as relays, contactors, thermistor relays, motor protection relays, motor starters, fses, timers, conters, signal lamps, start/stop bttons, varios sensors etc. 3.2 Control System Devices In this section, control devices will be explained. There are so many control devices. So that basic devices or eqipments will be introdced Electrically Controlled Switches a Contactors Contactors are sefl in commercial and indstrial applications, particlarly for controlling large lighting loads and motors. One of their hallmarks is reliability. However, like any other device, they are not infallible. Usally, the reason for contactor failre is misapplication. When someone ses a lighting contactor in a motor application, which is a misapplication. The same is tre when someone ses a "normal operation" motor contactor for motor jogging dty. Contactors have specific designs for specific prposes. Contacts will overheat if they transmit too mch crrent, if they do not close qickly and firmly, or if they open too freqently. Any of these sitations will case significant deterioration of the contact srface and the shape of that srface. Coils can overheat if operating voltages are too low or too high; if the contacts fail to open or close becase of dirt or misalignment; or if they have sffered physical damage. The following figre shows the interior of a basic contactor. There are two circits involved in the operation of a contactor: the control circit and the power circit. 38

48 The control circit is connected to the coil of an electromagnet, and the power circit is connected to the stationary contacts. Mo,vl'lble Contats Pov,ler Cilrctt Spting Coil Contacts Figre 3.1 Contactor Internal Strctre When power is spplied to the coil from the control circit, a magnetic field is prodced magnetizing the electromagnet. The magnetic field attracts the armatre to the magnet, which in trn closes the contacts. With the contacts closed, crrent flows throgh the power circit from the line to the load. When the electromagnet's coil is de-energized, the magnetic field collapses and the movable contacts open nder spring pressre. Crrent no longer flows throgh the power circit. Control Conm::il Signal Figre 3.2 Contactor Operation Principle 39

49 3.2.1.b Relays Relays are similar to contactors as operation principle. Relays operate tilizing electromagnetic principles. A simple electromagnet can be fashioned by winding a wire arond a soft iron core. When a DC voltage is applied to the wire, the iron becomes magnetic. When the DC voltage is removed from the wire, the iron retrns to its nonmagnetic state. This principle is sed to operate electromagnetic switches. A relay operates when the voltage is applied to the coil terminals. When a relay is energized, the palette is attracted by the core de to electromagnetism and closes N/0 contact and opens N/C contact. Relays are manfactred in different sizes and different operating voltages. Relays control low power electrical devices. Typical nominal voltage ratings (of coil) are 5VDC, 12VDC and 24VDC. Relays typically have a Normally Closed (NC) contact and a Normally Open (NO) contact. A relay consists of three parts: Electromagnetic parts (core and coil) Palette Contacts COIL I SPRING CORE~- --PALETIE --CONTACTS CORE CONTACTS COIL NOT ENERGIZED COIL ENERGIZED Figre 3.3 Relay Internal Strctre and Operation Principle 40

50 3.2.2 Fses Fses are protective devices which operate when the crrent exceeds specified limits at a satrated dration. Normally, crrent can be ndlating in short time intervals. When the crrent exceeds the limits for enogh time, fse stops crrent flow, removing the power from the load. Fses are manfactred in varios types bt miniatre circit breakers (MCB) are so poplar becase of being long life and practical. NH fses (knife fses) are being replaced with compact switches which can control high crrents sch as 320A, 630A easily a Miniatre Circit Breakers(MCB) Miniatre circit breakers (MCB) have a variety of application places sch as hoses, bildings, factories, etc. They are manfactred at rated crrent vales of A. They are manfactred as 1 pole, 3 poles (30 line) and 4 poles (for 30 line and a netral line). Short-circit ct-ot coil Inpt Terminal Otpt Terminal arc blow. nit Stationary. Contacts Figre 3.4 Varios MCBs and MCB Internal Strctre 41

51 3.2.3 Psh Bttons Psh bttons are sed to start/stop other control devices (contactor, relay, solenoid, valve, etc.) or send electrical signal to PLC or any other electrical control nits. There are two types of pshbtton, the momentary and maintained. The momentary pshbtton switch is activated when the btton is pressed, and deactivated when the btton is released. The deactivation is done sing an internal spring which separates two terminals electrically. The maintained pshbtton activates when pressed, bt remains activated when it is released. Then to deactivate the btton, it mst be pressed again. There are three kinds of momentary psh bttons: 1- Start btton 2- Stop btton 3- Two-way btton (jog) a Start Btton Start btton is sed to start the electrical control sytem or control circit. It is a normally open (NO) contact. It lets the power flow when it is pressed and it does not allow when it is released. L Q 0 1? 1 'i ;.. J it ANSI-Norm DIN-TSE Norm Figre 3.5 Start Btton Symbol b Stop Btton Stop btton is sed to stop the control circit or any device (motor, timer, etc.). It is normally closed (NC) contact and internal spring holds the contact terminals closed. When stop btton is pressed, it stops power flow ntil it is released. Q ~ bl ANSI Norm DIN-TSE Norm Figre 3.6 Stop Btton Symbol 42

52 3.2.3.c Two -Way Btton Two-way bttons are sed in the applications that when a device is started another device is needed to stop. It has a normally open (NO) contact and a normally closed (NC) contact. The two contacts operate inversely. When one of them is on, another off and vice versa. A I 13 I 14 I Q I ANSI Norm DIN-TSE Norm Figre 3.7 Two-Way Btton Symbol Figre 3.8 Varios Psh Bttons Signal Lamps Signal lamps are sed to indicate whether a device is operating or not or failed. They can be sed as warning eqipment between the machine and the operator in the control panel. Signal lamps are manfactred in different colors; red, yellow, orange, green. The blb is a neon lamp that can be Swan or Edison type with V operating range. F'AlLUHE: JIC - ANSI NORM DIN - TSE NORM Figre 3.9 Signal Lamp Symbols 43

53 3.3 Sensors A sensor is a device for detecting and signaling a changing condition. A changing condition can be simply the presence or absence of an object or material (discrete sensing). It can also be a measrable qantity like a change in distance, size or color ( analog sensing). This information, or the sensor's otpt, is the basis for the monitoring and control of a manfactring process Sensor Characteristics/Specifications When specifying sensors, it is important to nderstand the common terms associated with the technology. While the exact terms differ from manfactrer to manfactrer, the concepts are globally nderstood within the indstry a Sensing Distance When applying a sensor to an application nominal sensing distance and effective sensing distance mst be evalated. Nominal sensing distance is the rated operating distance for which a sensor is designed. This rating is achieved sing standardized criteria nder average conditions. The effective sensing distance is the actal sensing distance achieved in an installed application. This distance is somewhere between the ideal nominal sensing distance and the worst case sensing distance b Hysteresis Hysteresis or differential travel is the difference between operate (switch on) and release (switch off) points when the target is moving away from the sensor face. It is expressed as a percentage of the sensing distance. Withot sfficient hysteresis a proximity sensor will continosly switch on and off, or "chatter," when there is excessive vibration applied to the target or sensor. It can also be made adjstable throgh added circitry. Opera.tin!.! Point r= I Off D r1 [ l Object L.J Drap-aiUt Point Distance y Travel [)cistance mstance "y'-distance Distance "x" "x" =%d!ilferential Figre 3.10 Hysteresis and Parameters 44

54 3.3.1.c Repeatability Repeatability is the ability of a sensor to detect the same object at the same distance at all times. Expressed as a percentage of the nominal sensing distance, it is based on a constant ambient temperatre and spply voltage d Switching Freqency Switching Freqency is the nmber of switching operations per second achievable nder standardized conditions. In more general terms, it is the relative speed of the sensor. Moton Direc.~ T,g,etsof Fe 350' or A570' Gradee:l6 Figre 3.11 Standardized Switching Freqency Setp e Response Time The response time of a sensor is the amont of time that elapses between the detection of a target and the change of state of the otpt device (ON to OFF or OFF to ON). It is also the amont of time it takes for the otpt device to change state once the target is no longer detected by the sensor. The response time reqired for a particlar application is a fnction of target size and the velocity at which it passes the sensor Sensor Power Ratings For voltages are typically available to power indstrial sensors: 12VDC - 24VDC - 120V AC - 240V AC. Indstrial sensors are typically designed to operate within one of for voltage ranges: 10-30VDC, VAC, VAC, and V AC/DC. AC sensors and switches can receive power directly from the power line or a filtered sorce helping to eliminate the need for a separate power spply. Most DC sensors reqire a separate spply that isolates the DC portion of the signal from the AC line. 45

55 Typical crrent ratings for each sensor type: Photoelectric 35mA Ultrasonic 70mA Indctive 15mA Capacitive 15mA Sensor Otpt Configration Otpt configrations fall into two categories, electromechanical and solid-state. Solidstate otpts shold be considered for applications that reqire freqent switching or switching of low voltages at low crrents. Only transistor otpt will be explained. Solid-State or Electronic Otpts Transistor Field Effect Transistor (FET) Triac Analog Network or Bs a Transistor Otpt There are two kinds of transistor otpts: NPN and PNP types of otpts. For an NPN transistor otpt, the load mst be connected between the sensor otpt and the positive (+) power connection. This is also known as a 'sinking' otpt. A PNP transistor otpt is considered a 'sorcing' otpt. The load mst be connected between the sensor otpt and the negative (-) power connection. + NPN Transistor otpt PJ\JP Transistor Otpt Figre 3.12 NPN and PNP Transistor Otpt Connections 46

56 3.3.4 Indctive Proximity Switches Indctive proximity sensors are sed to sense metal objects. Indctive proximity sensors are operated sing an Eddy Crrent Killed Oscillator (ECKO) principle. This type of sensor consists of for elements: coil, oscillator, trigger circit, and an otpt. The oscillator is an indctive capacitive tned circit that creates a radio freqency. The electromagnetic field prodced by the oscillator is emitted from the coil away from the face of the sensor. The circit has jst enogh feedback from the field to keep the oscillator going.,.., I \ ~.ooa= Ele~dca!Coil CscilJator 'lolta~~ Re9i:ator. ~----To Load Figre 3.13 Indctive Proximity Switch and Operation Principle When a metal target enters the field, eddy crrents circlate within the target. This cases a load on the sensor, decreasing the amplitde of the electromagnetic field. As the target approaches the sensor the eddy crrents increase, increasing the load on the oscillator and frther decreasing the amplitde of the field. The trigger circit monitors the oscillator's amplitde and at a predetermined level switches the otpt state of the sensor from its normal condition ( on or off). As the target moves away from the sensor, the oscillator's amplitde increases. At a predetermined level the trigger switches the otpt state of the sensor back to its normal condition ( on or off). 47

57 3.3.5 Capacitive Proximity Switches Capacitive proximity sensors are similar to indctive proximity sensors. The mam difference between the two types is that capacitive proximity sensors prodce an electrostatic field instead of an electromagnetic field. Capacitive proximity switches will sense metal as well as nonmetallic materials sch as paper, glass, liqids, and cloth. The sensing srface of a capacitive sensor is formed by two concentrically shaped metal electrodes of an nwond capacitor. When an object nears the sensing srface it enters the electrostatic field of the electrodes and changes the capacitance in an oscillator circit. As a reslt, the oscillator begins oscillating. The trigger circit reads the oscillator's amplitde and when it reaches a specific level the otpt state of the sensor changes. As the target moves away from the sensor the oscillator's amplitde decreases, switching the sensor otpt back to its original state. I.. Targs1t r '''\1111/'' /)./ \\Hr/. ~ \\ r Ir. tlirh 1Lt 'ru?.~.. +4 D1,1bcttic. Plat.a --,-- Figre 3.14 Capacitive Proximity Switch Operation Principle Standard targets are specified for each capacitive sensor. The standard target is sally defined as metal and/or water. Capacitive sensors depend on the dielectric constant of the target. The larger the dielectric nmber of a material the easier it is to detect. The advantages of capacitive proximity sensors inclde: 1. Detects metal and nonmetal, liqids and solids 2. Can "see throgh" certain materials (prodct boxes) 3. Solid-state, long life 4. Many monting configrations 48

58 The disadvantages of capacitive proximity sensors inclde: 1. Short (1 inch or less) sensing distance varies widely according to material being sensed 2. Very sensitive to environmental factors-hmidity in coastal/water climates can affect sensing otpt 3. Not at all selective for its target Photoelectric Sensors All photoelectric sensors operate by sensing a change in the amont of light received by -- a photodetector. The change in light allows the sensor to detect the presence or absence of the object, its size, shape, reflectivity, opacity, translcence, or color. Photoelectric sensors provide accrate detection of objects withot physical contact. A light sorce sends light toward the object. A light receiver, pointed toward the same object, detects the presence or absence of direct or reflected light originating from the sorce. Detection of the light generates an otpt signal for se by an actator, controller, or compter. The otpt signal can be analog or digital. Some sensors modify the otpt with timing logic, scaling, or offset adjstments. A photoelectric sensor consists of five basic components: Light sorce Lightdetector Lenses Logic circit Otpt light Sorce (LEO:J Un:l'lt Det:ec!or \I I -- I :::t Logic Gtrclt Otpt Figre 3.15 Photoelectric Sensor Components 49

59 Table 3.1 Photoelectric Sensors Comparison Sen~ing Mode Appllcatiotts Advarltages Catioh$ Genefa1 prpqs. tsen,sirig,, Parts cotiriting Hglrmargl{l f-0rcontimm~ted B!)Jiiron~nts,. :!.11p~fsensing:(listances. '. Not a!fe(le<i:bfsecnm srfaca reflectoos., Pronab~n,rni reiiabe ~4lenyo h<i~ l]ighlyjeffect[ve.gbjects :114!)ra' ex~nst,,e: batasesepamte e arfreceiverreqirert,,.- - tlj,wi~; Alignment npcirtant. A1f9]d detecting obj d5 of dear matenat S'Mltwt,1,1,tl Retrorefleclw,e. General prpose sensing. ' Moderate SSl1S1t1@ illstantes Le~ expensne than transmifled oeam 1:e;asiH,imptr: winng Eas:y alig1!:1enl. General PUl'I'OSe sepsing of. shiny obj ets ' r~es lir$l srface. reflections IJ5e$ v1sib1e fed beam tor ease or lllfghl'neril Shorter.sensing distance titan transn111ted beam less margin than transmitlea beam. May detect rellecti~ from shiny objects {se polarized instead} Snorter sensing dis1af:li;e ttmn. Sfand<ll'd.Jelroreilective... May see second smface refleciions. Standard Appltcattons y.rhere both sides. ofthe objec:t ca:nnot be accessed Attess Jo 1irAl:H1itles tit the ob.ject ftqt reqired.... ~ore~cior neede~ ~ E~.of afig:~ment Cm1 re dil!lcll lo apply ii ihe grond behimhhe object is. simciently ref)ecfive aod wse tq the object.. Sharp Ctoff 01ffse 8hort-rang e detect.km of objects wtm thtn,eed to lgillw~ dos.(l dt;;r.an'c~ hackgronds General prpose sensing Areas where yo need to ignore backgronds that are dose to the ol:!ject t Acces.s lo tjolh sides of the object aol reqired PrQliides pn'.l!ec!iort against sensing of cf!}~ backgronds.. Detects objects rega:rd'kiss cl colqr within ~.fled Access to ooth Sides of B1e target not reqired.. fg:nores oac:~ronds beyond raled sen.s,illg dtsla111:e regardless of rellectilley Delea. o:bjects regardless of color at S!)ecified distance Only.sef11l tor very slw.rtmstance ;sensing Mom expensivet!jan otjier~jl)es of diffse sensors -. limited ninximm sensing distance. Ffxetj D.lffse Detection of small obj eets Detects objects at a specillc cltstance from sensor Detection of color marks Ad::rate detection otsmall objects in llspectffc tocairon Very sllorl distance sensfng Not sitable for general prpose sensing Object nill'si te accrat~ly positioned Wide D:Jifose Detection of objects not a ccrntely postttoned Detection of very fine threads over a broad area Good a!. ignoring, badgmnd re~e:tbns Detecting obj?cls that are not accrately posjtionecl t~o refledor needed Snort dlsiance sensing Fiber Alh1ws phetoelectrtc senslng in areas where a sensor cannot be monted becase of stze or envtronment considerations. Gfass fiber optlc cables zr;ailabfe fo:r:high amtlienl temperatre applications Shock and vibration resistant Plastic fiber opfic cables can oe sed in areas 'htle:re ronfaio?. nmemenl ls reqired fnsertin limitecl space Noise i111mn~y corrosive aeas placement More ex~nstll'e than lensed sensors Sharl-range 5Bt\c'5ing 50

60 Figre 3.16 Photoelectric Sensors 3.4 Brshed DC Motor Brshed DC motors are widely sed in applications ranging from toys to psh-btton adjstable car seats. Brshed DC (BDC) motors are inexpensive, easy to drive, and are readily available in all sizes and shapes. The constrction of a simple BDC motor is shown in Figre All BDC motors are made of the same basic components: a stator, rotor, brshes and a commtator. The following paragraphs will explain each component in greater detail. ~ c:: Br~"'1~, I i Commtator Fi"1d. I+ Magin\{ '" Corl Figre 3.17 Simple Two-Pole Brshed DC Motor Stator The stator generates a stationary magnetic field that srronds the rotor. This field is generated by either permanent magnets or electromagnetic windings. The different types of BDC motors are distingished by the constrction of the stator or the way the electromagnetic windings are connected to the power sorce. 51

61 3.4.2 Rotor The rotor, also called the armatre, is made p of one or more windings. When these windings are energized they prodce a magnetic field. The magnetic poles of this rotor field will be attracted to the opposite poles generated by the stator, casing the rotor to tm. As the motor trns, the windings are constantly being energized in a different seqence so that the magnetic poles generated by the rotor do not overrn the poles generated in the stator. This switching of the field in the rotor windings is called "commtation" Brshes and Commtator Unlike other electric motor types (i.e., brshless DC, AC indction), BDC motors do not reqire a controller to switch crrent in the motor windings. Instead, the commtation of the windings of a BDC motor is done mechanically. A segmented copper sleeve, called a commtator, resides on the axle of a BDC motor. As the motor trns, carbon brshes slide over the commtator, coming in contact with different segments of the commtator. The segments are attached to different rotor windings; therefore, a dynamic magnetic field is generated inside the motor when a voltage is applied across the brshes of the motor. It is important to note that the brshes and commtator are the parts of a BDC motor that are most prone to wear becase they are sliding past each other. 3.5 Conveyor Carrying System Application Conveyor systems are widely sed in indstry, especially in factories as prodct processing, packaging, conting, carrying applications. Conveyor systems are vitally important for mass-prodction in indstry. A conveyor has three parts: Belt, rotating roller and rotating part (motor fastened roller). Belt is stretched and placed on the top of rotating roller and rotating part. Rotating roller is a tblar shape polyamide or plastic solid which is penetrated into a cylindrical metal body from both tips. Ths, roller slides with belt as motor trns over to move the belt. 3.5.a Conveyor Operation and Control Starting/Stopping the Conveyor Operator or ser can control the conveyor by sing the control panel. Control panel has the following eqipments monted on the srface: Start/Stop and Replace bttons; red, 52

62 yellow and green indicator lamps. Red signal lamp is for warning, yellow and green lamps are for Motorl and Motor2 operation indication respectively. When "Start Btton" is pressed, "Warning Lamp" starts blinking for ten seconds and it stops. It alerts that "Beltl" is going to start soon. After ten seconds, "Motor I" starts operation and "Beltl" starts moving. When "Stop Btton" is pressed, all motors and indicator lamps go off immediately. Normal Operation "Motorl" starts to rotate the "Beltl" and the prodct moves on the belt. When the prodct passes front of "Sensorl" sensing face, it is sensed by the sensor. After 1 second, "Motorl" stops and starts again a second later. After the prodct is sensed by the "Sensorl ", "Motor2" starts after 3 seconds. So that, the prodct will not be shaken on the second belt. After the prodct is sensed by the "Sensor2", "Motor2" stops 1 second later. "Sensor2" also performs conting fnction and when 6 prodcts fall into the package, the two belts stop immediately to avoid overloading the package. "Warning Lamp" is lit and it indicates that the package is fll. Operator changes the package and pressing the "Replace Btton", conveyor retrns back to beginning operation. Figre 3.18 Conveyor Control System View 53

63 3.5.b Ladder Logic Program Netwi'.rk '1...,s{Ji; ~ipjf~1, I I ~~r~f~,t;:, \~ :fi~jj@c';~tq;fs~i~i LJ '\j7 />=IT I!/ I. I :_.~. d f _J ' Netvior k 8.J TIME,OEl.::'AY' FO,F~ilNA.RNING;:lJ'!i,JP,r;ihl;l{MOJ'OR1:,,,'}T,AF.J:TIME.. (10: ct.<ac.s>atter,:st~r!'.j!l:~9'r\' pr~sse~j fj ' :,:,?,'. i~o:j t tiij\;.s:f*4:: warning: T37 T38. 1 >' 1 l.:_ _> _.=,."'. J i:;, I 1 }, ;JJo,~c MO.O \,t>.i!o;!qr)> 'r3s T38 >=l t letwor.k 13 j'iojo.r1 PPEBATION.(tt after T38 T39 MO.O F'T Motor2 3.+JO.... ' t lety:ir.:ir'k.7 Tltv1E DELAY ',; ' ', ;- Sensor1 r{2 IN TON 54

64 NM\,i6rf's 132 M0.1 ==IJ (., R ') 11 I~~:, i ') }1 <' 1le. _.. n/o_..":r. -~~~,T39.. ::;r;;,r.. 1 : Neh.v6fk.:10.,$e~sd~; +10\,lpr; t~hlv,odc1} MO 0 Sto.p I {. p ).1 Mtrf1 R ) 1 'ENp) NOTE2: Programmers can appoint labels sch as "Start", "Stop", "Motor I", etc. instead of inpt/otpt bits "10.0", "QO.O" in Micro WIN PLC Program, clicking on the pll-down men "View I Symbol Table" and filling the "Symbol Table". Above given program is wrong nless "Symbol Table" is filled as given below. This helps the ser to change the address parameters easily and focs on the program better. 55

65 Table 3.2 Symbol Table for the PLC Program SYMBOL TABLE: View I Symbol Table in MicroWIN 3.2 s PLC Software P Name Address Comment Start 10.0 "Start " label responds to Start Btton inpt to start the conveyor Stop 10.1 "Stop" label represents the Stop Btton inpt to stop the conveyor Replace 10.2 "Replace" label checks the contact states of Replace Btton to start the conveyor Sensor "Sensor1" determines position of obiect on the belts and arranoes start/stop time Sensor "Sensor2" determines position of object and performs conting fnction of objects M1 on QO.O "M1 on" activates/de-activates Yellow Signal Lamp for Motor1 operation indication M2 on Q0.1 "M2 on" sends siqnals to Green Lamp whether Motor2 is on or off Warning Q0.2 "Warning" otpt sends signal to Warning Lamp before Motor1 operation and when oackace is fll Motor1 Q0.3 "Motor1" otpt sends 24VDC voltage to related relay to start Motor1 Motor2 Q0.4 "Motor2" otpt sends 24VDC voltaqe to related relay to start Motor2 3.5.c Network Explanations NETWORKl Network 1 ~ r-r.,s): Start Stop ~+) M0:1 RepL,µ 1 Conveyor operation control starts with Networkl and when "Start Btton" is pressed, "Start" labeled normally open (N/0) contact becomes on, "M0.1" memory bit is set and "MO.1" enables the T3 7 TON type timer. T3 7 timer starts timing p and it provides 10 seconds delay for "Warning Lamp" operation. After 10 seconds, "Warning Lamp" will be off and "Motor l " will start to rotate "Beltl ". When predefined nmber of prodcts or objects dropped into package, conveyor system will stop all the motors and indicator lamps. Conveyor will start again after "Replace Btton" is pressed, so that "Replace" N/0 contact is parallel with "Start" contact in this manner. 56

66 "MO.O" memory bit will be reset in order to nlock the "Motorl" and "Motor2" operation. Otherwise, they will be off even we pressed "Replace Btton". Here, "Stop" N/0 contact will not allow conveyor start if "Stop Btton" is pressed at the same time. NETWORK2 r:iej,y1qt\z:t. l':3i,1;. "'(37 SM0::5: \fl/.arni~g +:r <($ ;:,.. '... t.;'l. I,, I ] I I CO, I ; ( ) In Network 2, warning process is performed. After "Start Btton" is pressed "Warning Lamp" blinks for 10 seconds and stops. This warning alerts the people that belt will start soon. After "Start Btton" is pressed, T37 timer starts timing p and "T37 >=I + l" contact is on and "Warning" otpt coil becomes on. "SM0.5" stats bit provides a clock plse that is on for 0.5 seconds and then off for 0.5 seconds for a cycle time of 1 second. It makes "Warning Lamp" on and off continosly with 0.5 second time intervals. After 10 seconds; T37 reaches to 100, T37 N/C contact is off and "Warning" coil is off; forcing the "Warning Lamp" to off-state. When the package is fll, CO conter bit will be on and CO conter's N/0 contact will be on. Ths, "Warning Lamp" will be on if the package is fll (CO crrent vale eqals to PV). NETWORK3 T37 MO.. J IIN TOtl I ~PT l When "Start Btton" is pressed "M0.1" will be set and T37 timer will start timing p. T3 7 is a 100 ms type timer and Preset Time (PT) vale is selected as "100" for 10 seconds delay. After 10 seconds, T3 7 timer will be on. 57

67 r Its N/C contact will be off to stop "Warning Lamp" (See Network2). NETWORK4 l '. -,:- N:etWo'l'k'4.. " "'' ''' ''":.,,:,-,. Vtlaifiin R... <T3i.. 1'38. t..to{q. J;,iciJ~F\1, l,<s.. l;,, 1,, ", e.~. \f:100:. 1:-32. :>~I i ; +:1,ir~B.,,'.?'tl ;~~t~,:,'t:20: In Network 4, "Motorl" control is performed. After 10 seconds from "Start Btton" pressing time and "Warning Lamp" is in off-state, "Motorl" will operate. This task is declared as N/C contact of "Warning" otpt series with "T37 >=I+ 100" contact. T38 N/C contact will be off after 1 second from "Sensorl" sensing time (See Network5). After "Motorl" stopped de to T38 N/C contact, it starts again by means of "T38 >=I +200" contact 1 second later. T32 is a lms type timer which arranges reset time of T37, T38 and T39 timers. After first prodct passed from both sensor faces, T38 and T39 timers contines timing. These timers have to be reset to be sed for second, third and other prodcts. Otherwise, timers never eqal to preset time or integer vale in comparison contacts, i.e. T38 N/C contact, "T38 >=I +20" contact and start/stop timing of motors will not work properly. "T32 >=I + l" contact prevents "Motor l " and "Motor2" stop when the timers are reset de to "T32 ==I +2" contact in Network 8. MO.O memory bit will be on when 6 objects dropped into package and its N/C contact will not allow "Motor l" and "Motor2" to operate when the package is fll. Also, T3 8 and T39 timers will not perform timing depending on "Sensorl" and "Sensor2" otpt states; maybe other objects are in front sensors. 58

68 NETWORKS N~Vtofk 5 13:2 Sen,sot;1 T38 l ln TON I T38 HO H'T I >=] +'f In this network, "Motorl" and "Motor2" start/stop timing is provided sing T38 timer. When "Sensorl" senses the object, it resets T38 and T39 timers first (T32 N/0 contact and "Sensorl" N/0 contact is placed for this aim). Then, T38 timer starts operation to stop "Motorl" after 1 second from "Sensorl " sensing time and restart again after 1 second. In the third second, "Motor2" starts to rotate "Belt2" de to "T38 >=I +30" contact in Network6. "T38 >=I+ 1" contact is necessary for locking process and it does not let timer to stop when the object passed front of sensor. NETWORK6 Net,.,.,'Ork s. rss T39 Mo;o. Mott,'i' >=I I I I I I j t'.... ) M:2'-on ) In Network 6, "Motor2" control is performed similar to "Motorl" operation principle. When the object passes front of "Sensorl ", T38 timer starts timing p and "Motor2" starts to rotate "Belt2" 3 seconds later de to "T38 >=I + 30" contact. "Motor2" stops after the object passed front of "Sensor2" a second later (with T39 N/C contact). It starts again if an object is sensed by "Sensor l ". "M2_ on" otpt coil represents the otpt to indicate that "Motor2" is on. This otpt spplies a 24VDC sorce to tm on green signal lamp when "Motor2" is operating. When 6 prodcts dropped into package, MO.O memory bit is on and its N/C contact does not let power flow to the related relay's coil terminals (Al-A2) to stop "Motor2". 59

69 NETWORK7 N~ty}pr;J(t S,!'! nsorl T32 In this network, reset timing is provided sing a lms timer. As it is mentioned in Network4, T32 is a TON type timer and it arranges reset time of T38, T39 timers to be sed for the control of motors for the following prodcts or objects. The main reason for selecting a TON type timer is that when prodct passed front of "Sensorl", the timer mst be reset for next object process. Otherwise, extra programming techniqes wold be sed nnecessarily. NETWORKS Naj\voi{) et32 M0,1, '==rl ~- -~ ).1 Jif R ) itji C) t In Network 8, T38, T39 and M0.1 bits are reset. T38 and T39 timers are reset for the se of same timers to control both motors for next coming objects or prodcts. As yo see in Network 3, T37 timer is enabled with M0.1 memory bit and it is already set in the first network. If we reset T37 timer instead ofmo.l bit, T37 will restart timing again jst after reset occrred. So that, we needed to reset MO.I memory bit to stop T37 timer. 60

70 NETWORK9 ~rehvor,kis Senioi1 T39.r' >=I 1 MO.O T39 TON In Network 9, "Motor2" stop timing is provided. T39 timer is sed in this manner. When "Sensor2" sensed the object, T39 timer starts timing p and when preset vale is reached (after 10 seconds from object sensing time); N/C contact of T39 in Network 6 becomes off. Ths, Motor2 stops de to the activation of timer. Sensors natrally provide momentary otpt, timers need locking process. "T39 >=I + 1" contact is sed for this reason. When the package is fll, T39 timer is disabled to ensre correct operation of conveyor in the beginning operation. NETWORKlO r 14t.-;:6rt,1p :se.ns.o~ In this network, "CO" p conter conts the nmber of objects dropping into the package. When "Sensor2" is on for each time, conter's crrent vale increases one and when the nmber of objects in the package is eqal to 6 (depending on preset vale), "CO" conter is active. "CO" normally closed contact hinders the power flow to the motors (See Network4, 6), "Motorl" and "Motor2" is stopped. When "Replace Btton" is pressed "CO" conter is reset and it start conting from the beginning vale. 61

71 NETWORKll Stop... MQ\O 1 r i (;: S j t.16.1 R ) J In Network 11, conveyor stop operation performed. When stop btton is pressed, MO.O is set to stop all motors and indicator lamps de to N/C contact of MO.O bit. Also, it resets MO.l to stop T37 timer. These fnctions are also valid when package is fll (when CO is on). NETWORK12 This network terminates the main program sing the nconditional end instrction. It is necessary to se end instrction to declare to the assembler that the program finished. Otherwise, programming software will not compile the program and it will not be downloaded to the PLC. 62

72 CONCLUSION This project aims to present a practical atomation system sing the PLC as a control nit. PLC is sed for controlling and atomating the indstrial machines, indstrial process in prodction stages, etc. In this project, atomation task was the control of motors to move the conveyor belts and photoelectric sensors arrange the start/stop time of motors and performing the conting fnction of the prodcts in a packaging system. First of all, eqipments of control system were determined and their behaviors to the system were taken into accont. Correct types of eqipments were selected according to this evalation. PLC program was written considering all possible cases and clashes in great detail. Wrong programming strctres were abstained. Easy, simple programming techniqes were sed to avoid clashes, nexpected behaviors. Symbolic addressing was sed in programming to concentrate on the program deeply and sharply. Compare instrctions were sed to minimize the nmber of timers, conters as mch as possible. Ths, the nmber of networks was decreased srprisingly and the program memory was sed efficiently. Conseqently, a flexible PLC based control system was designed and the advantages, facilities and the convenience of Programmable Logic Controllers were observed and revealed. In any indstrial or real life application process, PLCs take great mission to control all the system. As a conclsion, PLCs are cheap according to their performance and fnctionality and offer flexible atomation soltions with less wiring, easy modification in the system and reliability becase of being microprocessor based device.

73 REFERENCES [1] Ozgr Cerna! Ozerdem, "Programmable Logic Controller and Programming", Near East University Press, [2] Information abot Micro PLCs " atomationdirect.com " [3] Information abot Large PLCs '' [4] Information abot IDEC PLCs '' idec. comlsenlprodcts/catalogs/p LCs/P LCsCategory.html'' [5] Information abot Relays and Control Devices Ltf Hayta, '' Elektrik Kmanda Devreleri ve Deneyleri '' [6] Information abot Siemens S Micro PLC. " '' SIMATIC S7-200 PLC System Manal pblished in 2001 [7] Central Processing Unit (CPU) Strctre of PLC Tim Wilmshrst, ''the Design of Small-Scale Embedded Systems'' (8] Information abot Brshed DC Motors Brshed DC Motor Fndamentals Application Note (AN905) Microchip Inc. [9] Sensors and Applications Fndamentals of Sensing Training Manal Rockwell Atomation/ Allen Bradley

74 Photoelectrics Diffse-reflective Type PD32CND50 CARLO GAVAZZI Miniatre sensor range Range: 500 mm Sensitivity adjstment by Teach-In programming Modlated, red light 660 nm Spply voltage: 10 to 30 VDC Otpt: 100 ma, NPN or PNP preset Make and break switching fnction programmable LED for otpt indication, signal stability and power ON Protection: reverse polarity, short circit and transients Cable and plg versions Compact hosing Excellent EMC performance Prodct Description The PD32CND50 sensor family comes in a compact 12 x 32 x 20 mm reinforced PM MA/ABS-hosing. The sensors are sefl in applications where highaccracy detection as well as small size is reqired. The Teach-In fnction for adjstment of the sensitivity makes the sensors highly flexible. The otpt type is preset (NPN or PNP), and the otpt switching fnction is programmable (NO or NC). Ordering Key Type ~ Hosing style ' Hosing size ' Hosing material ~ Hosing length ~ Detection principle ~ Sensing distance ~ Otpt type ' Otpt configration ~ Connection type ~ Teach-In ~ Type Selection Hosing WxHxD Range Sn Ordering no. NPN & PNP cable Make & break switching Ordering no. NPN & PNP plg Make & break switching 12 x 32 x 20 mm Specifications Rated operating distance (Sn) Blind zone Sensitivity Temperatre drift Hysteresis (H) (differential travel) Rated operational volt. (Us) Ripple (U,pp) Otpt crrent Continos (I.) Short-time (I) No load spply crrent (lo) Minimm operational crrent (Im) OFF-state crrent (I,) Voltage drop (Ud) Protection 500 mm PD 32 CND 50 NPT PD 32 CND 50 PPT Light sorce Light type Sensing angle Ambient light Light spot Operating freqency Response time OFF-ON (ton) ON-OFF (toff) Power ON delay (tv) Otpt fnction NPN and PNP NO/NC switching fnction Indication Otpt ON Signal stability ON and power ON Environment Installation category Polltion degree Degree of protection PD 32 CND 50 NPM5T PD 32 CND 50 PPM5T Specifications are sbjecto change withot notice ( ) 1

75 PD32CND50 CARLO GAVAZZI Specifications {cont.) Ambient temperatre Operating Storage Vibration Shock Rated inslation voltage Hosing material Body Front material Connection Cable Plg Weight CE-marking Approval Operation Diagram tv = - Power ON delay Power spply Object/target present Break (NC) Otpt ON Make (NO) Otpt ON Wiring Diagrams -- k%t AM/ ill 1-tv-l E rn,~ +t&i&i/mhmwm NPN PNP ---~1BN + r--- 3J3U - V I 48K I - L---l WH 1 3BU Teach inpt is active when 2 WH wire is connected to V+ (1 BN). Dimensions Cable version Plg version TEACH IN TEACH IN ~w rol 03.5 I I N n ~x1 I ~ Specifications are sbject to change withot notice ( )

76 PD32CND50 CARLO GAVAZZI Signal Stability Indication Signal level Accessories Monting bracket APD32-MB1 nme For frther information refer to "Accessories" Installation Hints To avoid interference from indctive voltage/ crrent peaks, separate the prox. switch power cables from any other power cables, e.g. motor, contactor or solenoid cables Relief of cable strain Protection of the sensing face Switch monted on mobile carrier ~ ~a: Correc~ The cable shold not be plled A proximity switch shold not serve as mechanical stop Any repetitive flexing of the cable shold be avoided Delivery Contents Photoelectric switch: PD 32 CND Installation instrction Packaging: Cardboard box Specifications are sbject to change withot notice ( ) 3

77 PD32CND50 CARLO GAVAZZI Adistment Sensitivity adjstment, with static object 1. Line p the sensor with the object. Yellow LED and green LED are ON. 2. Press the btton for 3 s ntil both LED's flash simltaneosly (the first switching point is stored). 3. Place the object otside the detection area. 4. Press the btton for 1 s. a) The green LED flashes and stays ON: the second switching point is stored, and the sensor is ready to operate. b) Both LED's flash simltaneosly: the sensor cannot detect the object, no switching points are stored. ~~3~~ CJ 3s 1s Programming of make and breaching fnction 1. Press the btton for 13 s. 13 s Both LED's flash alternately. 2. Release the btton: the green LED flashes. 3. While the green LED flashes, the otpt is inverted each time the btton is pressed. This is indicated by the yellow LED. When the btton is not pressed for 1 0 s, the crrent otpt fnction is stored. The sensor is now ready for operation. Defalt setting 1. No object in the detection area: Press the btton for 3 s, ntil both LED's flash simltaneosly. & 3 s 2. No object in the detectio& Press the btton for 1 s. 1 s The sensor is set to maximm sensitivity. NB! The Teach Inpt (2 WH) will work similarly to the psh btton, active High. Sensitivity adjstment, with only one object 1. Line p the sensor with the object. Yellow LED and green LED are ON. 2. Press the btton for 3 s ntil both LED's flash simltaneosly (the first switching point is stored). 3. Leave the object in the detection area, press the btton for 1 s. The green LED flashes and stays on: the second switching point is stored, and the sensor is ready to operate. Sensitivity adjstment, with a rnning process 1. Line p the sensor with the object. Green LED is ON. At this stage the stats of the yellow LED can be ignored. 2. The rnning process mst be the only "object" within the detection area. Press the btton for 3 s ntil both LED's flash simltaneosly. & 3s 3. Press the btton for at least the dration of one process cycle. & 1cycle a) The green LED flashes and stays ON: both switching points have been stored, and the sensor is ready to operate. b) Both LED's flash simltaneosly: the sensor cannot detect the object, no switching points are stored. 4 Specifications are sbject to change withot notice ( )

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