Simplification of engineering and precise control of manufacturing process can result in significant cost savings. The most cost-effective way, which can pay big dividends in the long run, is flexible automation; a planned approach towards integrated control systems. It requires a conscious effort on the part of plant managers to identify areas where automation can result in better deployment/utilization of human resources and savings in man-hours, down time. Automation need not be high ended and too sophisticated; it is the phased, step-by-step effort to automate, employing control systems tailored to one’s specific requirements that achieves the most attractive results. That is where Industrial electronics has been a breakthrough in the field of automation and control techniques.
ROLE OF ELECTRONICS IN AUTOMATION
A constant demand for better and more efficient manufacturing and process machinery has led to the requirement for higher quality and reliability in control techniques. With the availability of intelligent, compact solid state electronic devices, it has been possible to provide control systems that can reduce maintenance, down time and improve productivity to a great extend. By installing efficient and user friendly industrial electronics systems for manufacturing machinery or processors, one can obtain a precise, reliable and prolific means for generating quality products.
Considering the varied demand and increasing competition, one has to provide for flexible manufacturing process. One of the latest techniques in solid state controls that offers flexible and efficient operation to the user is “PROGRAMMABLE CONTROLLERS”. The basic idea behind these programmable controllers was to provide means to eliminate high cost associated with inflexible, conventional relay controlled systems. Programmable controllers offer a system with computer flexibility:
1. Suited to withstand the industrial environment
2. Has simplicity of operation
3. Maintenance by plant technicians and
4. Reduce machine down time and provide expandability for future.
DEFINATION OF PLC
A Programmable controller is a solid state user programmable control system with functions to control logic, sequencing, timing, arithmetic data manipulation and counting capabilities. It can be viewed as an industrial computer that has a central processor unit, memory, input output interface and a programming device. The central processing unit provides the intelligence of the controller. It accepts data, status information from various sensing devices like limit switches, proximity switches, executes the user
control program store in the memory and gives appropriate output commands to devices like solenoid valves, switches etc.
Input output interface is the communication link between field devices and the controllers; field devices are wired to the I/O interfaces. Through these interfaces the processor can sense and measure physical quantities regarding a machine or process, such as, proximity, position, motion, level, temperature, pressure, etc. Based on status sensed, the CPU issues command to output devices such as valves, motors, alarms, etc.
Programmer unit provides the man machine interface. It is used to enter the application program, which often uses a simple user-friendly logic.
BENEFITS OF PROGRAMMABLE CONTROLLERS
1. Programmable controllers are made of solid state components and hence provide high reliability.
2. They are flexible and changes in sequence of operation can easily be incorporated due to programmability. They may be modular in nature and thus expandability and easy installation is possible.
3. Use of PLC results in appreciable savings in Hardware and wiring cost.
4. They are compact and occupy less space.
5. Eliminate hardware items like Timers, counters and Auxiliary relays. The presence for timers and counters has easy accessibility.
6. PLC can control a variety of devices and eliminates the need for customized controls.
7. Easy diagnostic facilities are provided as a part of the system. Diagnosis of the external systems also becomes very simple. Thus easy service/maintenance.
8. Programming devices provide operator friendly interface with the machine. Being an outcome of the latest art of electronics technology, Programmable controllers provide higher level of performance with computers is possible. Useful management data can be obtained and maintained.
9. It has total protections against obsolescence and has wide scope for up gradation.
PLCs contain three basic sections:
1. Central processing unit (CPU).
2. Memory: EPROM, RAM, and so on.
3. Input/output section for communication with peripherals (ADC, DAC).