Plc & scada applications Role of Automation in Industry Benefits of Automation Necessity of PLC Definition of PLC History & Evolution of PLC Types of PLC Selection Criterion Overall PLC System PLC Input & Output Modules with Interface CPU Programmers Power Supplies Solid State Memory Advantages & Disadvantages of PLC

Role of Automation To Utilize the computers & controllers for controlling of process parameters To increase the reliability & efficiency of system by replacement of no. of employees with machines To increase the rate of production To reduce the costing of process To increase the quality of work.

Benefits of automation Increase in productivity Reduction in no. of Labour required Enhanced Accuracy of work Restless system operation Ease in data collection

Necessity of plc Gaining the control of manufacturing process Consistency of operation Improving the quality & accuracy Work in difficult & hazardous atmosphere Increase in productivity Inventory of the process Quick change in product.

Definition of plc PLC is the solid state member of computer family that uses IC’s instead of electromechanical devices to implement the control functions of a System/ Process.

History & evolution of plc The Hydramatic Division of the General Motors Corporation specified the design criteria for the first programmable controller in 1968. To eliminate the high costs associated with inflexible, relay-controlled systems. 1968 Programmable concept developed 1969 Hardware CPU controller, with logic instructions, 1K of memory and 128 I/Os 1974 Use of several (multi) processors within a PLC – timers and counters; arithmetic operations; 12K of memory and 1024 I/Os 1976 Remote input/output systems introduced 1977 Microprocessors - based PLC introduced 1980 Intelligent I/Os developed with communication facilities 1983 Low Cost Small PLC Developed 1985 Networking of PLCs, Computer & Machines with the SCADA system

Types of plc Micro PLCs : 32 I/Os Small PLCs : 32 to 128 I/Os Medium PLCs : 64 to 1028 I/Os Large PLCs : 512 to 4096 I/Os Very Large PLCs : 2048 to 8192 I/Os.

Selection criterion No. of I/Os Memory of CPU Scan Time Communication Availability of Program Software Special Arrangements such as distance between machine & panel Physical Environment

Overall plc system

Overall plc system

Input module

output module

Cpu Bitwise Performance Scan Time Diagnostics of System Control of Process Bitwise Performance Scan Time Diagnostics of System

Programmers – Mini programmers

Power supply As per rating of the PLC Also monitors & controls the supply voltage Sustain 10-15% tolerance Also has diagnostic feature Const Voltage Transformer Isolation Transformer

Solid state memory Executive Memory Area Application Memory Area ROM RAM PROM EPROM EAROM EEPROM

Advantages Flexibility Faster response time Implementing changes & Error Detection Lower Cost Large no of Contacts Pilot Running Visual Operation Easy Programming Reliability & Maintainability Documentation Communication Capabilities Small Size

disadvantages High Capital Investment Fixed Program Application Fail Safe Mode