History of Programmable Logic Controls
With emergence of new technologies, control engineering has undergone drastic changes. In the ancient days, only human beings could control a system. The 19th and 20th century witnessed great deal of advancement in technology. Electricity based on relays has been adopted for control systems. More recently the development of Programmable Logic Control (PLC) has added up to the advancing manufacturing controls. PLC has been widely used in industrial automation. The advent helps control and regulates sequence in any production operations. Notably, most production process undergo a fixed a logical steps. PLC has gained popularity in most industries and is expected to become predominant even in the future.
During early days of its inception, PLC was hard wired by use of logical units, timers and electronic relays. It restricted production time and it was hard for products to be changed. The system was not effective, and this forced engineers to invent a flexible PLC’s system. The pursuit for an effective control system started in 1970s. This was facilitated by the advent of mini-computers which allowed easy change of input-output features of a manufacturing process. In 1980s, fast and reliable microprocessors came into being. In effect, this facilitated the emergence of the current PLC’s. The instrument is robust and serves many functions. The system is available in small, medium and large sizes (Vernon 2010).
Units of a Programmable Logic Control
PLC has four distinct functional units. The system has a Programme Memory where the instructions and procedures for the logical steps of a manufacturing process are stored. The system has a Data Memory which carries interlocks, status of the switches and values of data. The output devices comprises of hardware and software drivers which are commonly used by the industrial process actuators which may include motors, valves and solenoid. The input device is another unit that has hardware and software drivers such as proximity detectors, switch status sensors and interlock setting. Other than the above mentioned units, Programmable Logic Control has a superior programming unit. In most cases, a PC may be connected to PLC to make a programming unit (Lewis 2008). The programming unit performs very crucial role during automated manufacturing process. It is used for building, testing and editing logical steps that to be followed during the manufacturing operations. PLC’s are programmed differently by different manufacturers using their own standards and definitions. The most programming languages used include Sequential Function Chart, IIEC 61131-3 standard and Function Block Diagrams. However, Ladder Logic is a programming language that has been well established and widely used by PLC programmers (Lewis 2008).
Functions of PLC System tools
The basic function of Programmable Logic System is to admit information from switches and sensors to control machines in a manufacturing process. It electronically rewires the established control panel thus facilitating relay of information. In the recent times, PLC roles have extended beyond mere relay of information in system circuits to food processing and environment control. The PLC communication tools, processing power and information treatment process have replaced desktop computer.
Advantages of using PLC
PLC has been widely used in most manufacturing industries because of its numerous advantages. Firstly, PLC is cost-effective for controlling sophisticated manufacturing processes and systems. Secondly, it is flexible hence can be used to control other complex systems easily. Thirdly, PLC has high computational abilities thus allowing a classy control of the manufacturing operations. PLC allows trouble shooting thus making programming easier. Due its reliable components, the system can operate for a long time without failure.
Disadvantages of Programming Logic Controls
The system is expensive to installed hence small companies would be able not utilize the invention. It requires technical expertise which might be lacking in most organizations.