What is plc?
Plc or programmable logical controllers was first introduced by the members of Bedford associates in 1968. The
plc systems were developed to provide a substitute for huge transmit based control panels.
These systems were very stubborn and they use to provide major replacement when the control sequence was about to get changed. The expansion of the micro processor since mid 70's has allowed Plc to take on complex issues and larger purposes as the processor speed is very high.
Industrial automation has played an important role in the development of the programmable logical controller systems. Engineers struggle to combine various mechanical devices with certain mathematical and managerial tools to create complex systems. These systems can be utilised for quickly mounting range of purposes and human activities.
Ladder logic
The Plc has to be maintained regularly by various technicians and stimulating recruits and to sustain this; the programming language of Ladder logic was developed. This is based on the relay and contact signs experts that were utilised to toss wiring figures of electrical control panels.
Till the time there wasn't any formal programming standard for Plc's, the introduction of IEC 61131 standards provided a much prescribed approach to the coding. The manufacturers of Plc have been very slow so far on the uptake of standard with biased functioning.
Scada and HMI
The traditional programmable logical controllers interfaced with the operators in a similar fashion as the relay control panel. It can be done via push- buttons and switches for control and lamps for indication.
With the introduction of personal computers or PC's in the 80's permitted the expansion of a computer based interface to the operators. These were 'simple supervisory control and data acquisition' or 'Scada' systems and recently via dedicated operator control panels called 'human machine interfaces' or 'HMI'.
Introduction to SCADA
It refers to an industrial control system that monitors processes which are industrial, infrastructural or facility based.
1 The industrial process includes manufacturing, producing, generating power, fabricating and taming. This may run in incessant, set, repetitive or distinct mode.
1 The infrastructural process can be public or private, and it also includes water treatment and distribution. Other than that, it also consists of wastewater collection and treatment, gas and oil pipelines and large communiqué systems.
2 Whereas, when it comes to the facility process it occurs both in public as well as private facilities. It includes buildings, airfields, ships as well as space stations. Other than that, they also check and manage HVAC as well as energy consumption.
This system mainly consists of the components which are its subsystems and they are:
1 HMI or Human machine interface,
2 A supervisory or computer system, that is useful in gathering information on the process and sending control back to the process.
3 RTU's or Remote Terminal Units.
