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Network Support For Programmable Logic Controller Problems

Programmable Logic Controller

Nowadays Programmable Logic Controller or PLCs are widely used in a lot of industries. These devices are basically industrial digital computers which are employed to monitor the inputs to the process and control the outputs based on the state of inputs. The primary objective of PLC is to automate machines or industrial processes like machinery control on a factory assembly lines, relay control, motion control, process control, distributed control, etc. There are numerous manufacturers in the market today, such as Alstom, ABB, Hitachi, Motorola, Panasonic, Siemens, Mitshubishi, etc, which not only produce state of the art PLCs but also provide excellent PC support to their products.

Definition
As per the definition by National Electrical Manufacturing Association, a PLC is defined as “A digitally operating electronic apparatus which uses a programmable memory for the internal storage of instructions by implementing specific functions such as logic sequencing, timing, counting, and arithmetic to control, through digital or analog input/output modules, various types of machines or processes”.

Brief History
Initially PLC was invented to meet the growing needs of the automotive manufacturing industry. Before advent of PLC, the complex industrial process was controlled by plenty of relays, dedicated closed loop controllers, drum sequencers and cam timers. The task of updating such huge control system was very cumbersome and costly. To overcome these shortcomings, digital computer was employed to regulate the industrial control process. GM Hydramatic, the automatic transmission division of General Motors, was the first company to call for a tender to replace its hard wired relay system in 1968. Bedford Associates won the bid and produced the first PLC in the market. It was named 084, since it was the 84th project of Bedford Associates. Since then thousands of PLCs have been launched in the market. All the manufacturers of PLCs provide extensive network support to their clients.

Development
The objective of the earlier version of PLCs was to replace the relay logic systems. A programming language called Ladder Logic was used to program those devices. Ladder Logic described the function by a graphical drawing of the circuit diagrams of the relay logic hardware. Later, many other traditional programming languages like Basic, C, etc. were developed to program the PLCs. Apart from traditional programming languages, state transition diagram based languages like State Logic is also used widely. Branded programming terminals were used to program the earlier versions of PLCs till the mid 1980s. Nowadays application software on PCs can directly program the PLCs through RS232, RS422, RS485, Ethernet ports. Assistance of a PC support provider could be taken to diagnose any problem in communicating with the PLCs through ports.

Applications
PLC is the main component of any process control system. Multiple PLCs could be connected to the main PC to control complex processes like motion control, distributed control system, networking, process control, sequential relay control, etc. In terms of communication, storage, data handling and processing capabilities, some of the latest PLCs could compete against a la mode PCs. Because of the extensive input/output design, PLCs could be connected to sensors and actuators without much hassle. Through sensors, PLCs could monitor process variables like pressure, temperature, switches position, etc. Magnetic relays, solenoids, pneumatic cylinders, electric motors could be controlled by the PLCs through actuators. For debugging the sensor and actuator problems, extensive network support is provided by the manufacturers of PLCs.

PC Support For PLC Problems
Designing, developing and debugging a complex process control system using Programmable Logic Controller is quite an arduous task, which could be made easier with the network support of PLC manufacturers. At present many third party vendors also provide extensive PC support for any type of PLC system problems.