Automation is necessary for manufacturing industry to improve productivity and cost efficiency. Programmable Logic Controller(PLC) is an industrial computer used for automating the manufacturing process. It is widely used in various industrial applications like assembly line applications, water tank quenching system, feeding control system,closed loop textile shrinkage system,etc. The user could program these devices to execute a sequence of events. These events are activated by inputs received at the PLC. Once an event occurs, an electronic control gear or switch is activated which initiates some specific actions on some external devices. The PLC will continuously monitor the inputs and control the outputs based on the conditions of the inputs. The manufacturers of PLC provide extensive tech support for the PLC problems in the field.
PLC programming or PLC programs are generally written on a desktop or laptop using some specific applications and then downloaded into the PLC through serial ports or network. The downloaded program is stored in flash memory or non volatile RAM of the PLC. A PLC could be programmed using several standard languages. As per IEC 61131-3 standard, five programming languages could be used for programming PLCs. Those five authorized languages are Sequential Function Chart, Structured Text, Ladder Diagram, Instruction List and Functional Block Diagram. Though all PLC manufacturers follow the common fundamental principles of PLC programming,but different memory mapping,input output mapping and instruction sets made one PLC incompatible with another. PC support for PLC programming problems is provided by the particular PLC manufacturer.
Sequential Function Chart
Sequential Function Chart or SFC is a graphical programming language,used to program PLCs. It is defined in the IEC 848 standard under the title of “Preparation Of Control Charts For Control Systems”. The basic components of SFC are – steps with related actions, state transition, relation between steps and state transition. In an SFC diagram, a step could be either inactive or active. Only active step’s actions are carried out. There are two reasons for activating a step. The first reason is that it is an initial one configured by the programmer. The second one is that it was triggered in the scan cycle and has been deactivated afterward. Steps could be triggered only after all the previous steps are made active. Writing a program using Sequential Function Chart is a quite difficult task for a beginner. In such cased the user should consult a veteran pc support provider.
Structured Text is a high level programming language, specifically used for programming PLCs. It is organized in blocks. IEC61131 standard defines the functions and variables. Manufacturers of PLCs provide some ready made programs written in Structured Text, which could be modified to suit the application of the user with help of a network support provider.
Ladder Diagram is a programming language which employs graphical diagram to describe a program visually. The graphical diagram is usually based on the relay circuit hardware. It has been developed particularly for writing program for PLCs. This is a very useful tool in developing simple as well as complex industrial control system. Sometimes Ladder Diagram is used along with Human Machine Interface(HMI) program which makes the process of automation much easier. Combining Ladder Diagram with HMI should be done by an experienced PC support provider.
Instruction List is a low level programming language. It is similar to Assembly programming language. The functions and variables are defined by IEC61131 standard. Program control flow could be changed by invoking functions or by using jump command. Writing complicated and lengthy PLC programs using Instruction List could be made easier with online tech support.
Function Block Diagram
Function Block Diagram is a graphical representation which depicts the relation between the input and output variables. The whole system is described as a set of blocks. All input and output variables are linked to the blocks by connection wires. Function Block Diagram for complex systems could easily be implemented with experienced Dell support.