PLC & SCADA

Introduction to PLCs:-

A programmable logic controller (PLC)  or programmable  controller is  an  industrial digital  computer which has been adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis.
They were first developed in the automobile industry to provide flexible and easily programmable controllers to replace hard-wired relays, timers and sequencers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a "hard" real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

 BRANDS OF PLCs :-

•  Allen Bradley PLCs (AB) 
•  ABB PLCs (Asea Brown Boveri). 
• Omron PLCs. 
•  Mitsubishi PLCs. 
•  Hitachi PLCs. 
•  Delta PLCs. 
• General Electric (GE) PLCs

ADVANTAGES OF PLCs:

•  No hard wire requirement. 
•  Cost reduced. 
•  Efficiency increased 
• Easy maintenances 

 APPLLICATIONS OF PLCs:- 

• Industry:-oil plant, gas,cemant,automoblie,manufacturing companies, chemical,power  genration. 
•  It is used in travel industry for escalator operation, monitored safety control system.

 TYPES OF PLCs:-   

 There are two types of PLCs: 

•  Compact or Fixed or Non modular:- We cannot change and modify input-output.  
•  Modular:- We can change and modify input output. 

.Timer:-

There are types of timer:- 

(a) S_PULSE:- If the signal state of input I0.0 changes from "0" to "1" (positive edge in RLO), the timer T5 will be started. The timer will continue to run for the specified time of two seconds (2 s) as long as I0.0 is "1". If the signal state of I0.0 changes from "1" to "0" before the timer has expire the timer will be stopped. If the signal state of input I0.1 changes from "0" to "1" while the timer is running, the time is reset. The output Q4.0 is logic "1" as long as the timer is running and "0" if the time has elapsed or was reset.
   

(b) S_PEXT: - If the signal state of input I0.0 changes from "0" to "1" (positive edge in RLO), the timer T5 will be started. The timer will continue to run for the specified time of two seconds (2 s) without being affected by a negative edge at input S. If the signal state of I0.0 changes from "0" to "1" before the timer has expire the timer will be re-triggered. The output Q4.0 is logic "1" as long as the timer is running. 

(c) S_ODT:- If the signal state of I0.0 changes from "0" to "1" (positive edge in RLO), the timer T5 will be started. If the time of two seconds elapses and the signal state at input I0.0 is still "1", the output Q4.0 will be"1". If the signal state of I0.0 changes from "1" to "0", the timer is stopped and Q4.0 will be "0" (if the signal state of I0.1 changes from "0" to "1", the time is reset regardless of whether the timer is running or not).

 Introduction to SCADA:- 

Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high level process supervisory management, but uses other peripheral devices such as programmable logic controller (PLC) and discrete PID controllers to interface with the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA computer system. However, the real-time control logic or controller calculations are performed by networked  modules  which  connect  to  the  field  sensors and actuators. 

 NEED OF SCADA:- 

• Previously without SCADA an industrial process was entirely controlled by PL, CNC, PID & micro controllers having programmed in certain languages or codes.
•  These codes are either written in assembly language or relay logic without any rue animation that would explain the process running.
•  Thus to make the understanding process easily with the help of rue animation SCADA came in existence.

 FEATURES OF SCADA:- 

• Dynamic process control
•  Alarm
• Security
•  Excel communication
•  Recipe management
• Script
• Trends

INTOUCH WONDERWARE SCADA :-

Introduction:-Wonderware is a brand of industrial software sold by Aveva. Wonderware software is used in diverse industries, including: Automotive Assembly, Facilities Management, Food and Beverage, CPG, Mining and Metals, Power, Oil and Gas, Chemicals, Energy, and Water and Wastewater.