Introduction to Programmable Logic Controllers (PLCs) and SCADA Systems, Thesis of Very large scale integration (VLSI)

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TABLE OF CONTENTS

CHAPTERS TITLES PAGE.NO

1 INTRODUCTION TO PLC 4 - 5

2 PLC PROGRAMMING LANGUAGES 6 - 8

3 SCADA SYSTEM 9 - 14

4 RESULT 15

5 CERTIFICATE 16

LIST OF FIGURES

• 1.1 Type of PLC’s FIGURE NO FIGURE NAME PAGE.NO
• 1.2 Fixed Type PLC
• 1.3 Modulator Type PLC
• 1.4 Rack Type PLC
• 2.1 PLC Architecture
• 2.2 PLC – CPU unit
• 2.3 Connecting PLC with PC
• 3.1 SCADA Unit
• 3.2 Hardware Architecture
• 3.3 Software Architecture
• 3.4 Remote industrial Plant
• 3.5 Data Acquisition System
• 3.6 Generalised Data Acquisition System
• 3.7 Signal Channel DNS
• 4.1 Light Intensity LDR OFF
• 4.2 Light Intensity LDR ON

Types of PLCs

The general classification of PLC based upon the number of input and outputs is:

• Fixed type PLC
• Modular type PLC
• Rack type PLC / Distributed PLC Fig 1.1: - Types of PLCs

Fixed Type PLC

In this type of PLC all the components of the PLC are as a single unit. The number of I/O supported by the PLC is decided by the manufacture and cannot be changed. This type of PLC can support a small number of I/Os. Some examples of fixed PLC types by different manufacturers and the terminology they use is:

• Allen Bradley PLC – Micro
• Omron PLC – Compact
• Siemens PLC – Basic
• Delta PLC – Standard
• Koyo PLC – Brick Fig 1.2: - Fixed type PLC

Modular Type PLC

Modular PLC is divided by compartments into which separate modules can be plugged. This feature greatly increases the options and the unit’s flexibility. Mixing the different types of modules according to the desire is possible. In modular type PLC the number of I/Os can be increased by the addition of modules to the existing PLC. Fig1.3: - Modular Type PLC

Rack Type PLC

In Rack type PLC all the components of the PLC are as separated modules and are assembled to form one unit by mounting the individual components on a rack. This PLC can support up to thousands of I/Os. Fig 1.4:

Fig 2.1: - PLC Architecture

PLC – CPU unit

The CPU controls and supervises all operations within the PLC, carrying out programmed instructions stored in the memory. An internal communications highway, or bus system, carries information to and from the CPU, memory and I/O units, under control of the CPU. Virtually all modern PLCs are microprocessor- based, using a 'micro' as the system CPU. Some larger PLCs also employ additional microprocessors to control complex, time-consuming functions such as mathematical processing, three- term PID control, etc. Fig 2.2: PLC – CPU unit

Connecting PLC with PC:

PLC controller is linked with a PC computer through an RS-232 cable. One end of the cable is connected to a serial PC port (9-pin or 25-pin connector), while the other end is connected to an RS-232C connector on RS232 module of a CPM1A controller. In order to establish a connection with a PC, DIP switch on the connector must be set in "Host" position. Fig 2.3: Connecting PLC with PC

received by the RTU, it applies the electrical signal to relays. Most of the monitoring and control operations are performed by RTUs or PLCs. Fig 3.2: - Hardware Architecture

Software Architecture

Most of the servers are used for multitasking and real-time database. The servers are responsible for data gathering and handling. The SCADA system consists of a software program to provide trending, diagnostic data, and manage information such as scheduled maintenance procedures, logistic information, detailed schematics for a particular sensor or machine, and expert-system troubleshooting guides. This means the operator can see a schematic representation of the plant being controlled. EX: alarm checking, calculations, logging, and archiving; polling controllers on a set of parameters, those are typically connected to the server. Fig 3.3: - Software Architecture

Working Procedure of SCADA system The SCADA system performs the following functions:

• Data Acquisitions
• Data Communication
• Information/Data presentation
• Monitoring/Control Data Acquisitions: The real-time system consists of thousands of components and sensors. It is very important to know the status of particular components and sensors. For example, some sensors measure the water flow from the reservoir to the water tank and some sensors measure the value pressure as the water is a release from the reservoir. Data Communication: The SCADA system uses a wired network to communicate between users and devices. Real-time applications use a lot of sensors and components which should be controlled remotely. The SCADA system uses internet communications. All information is transmitted through the internet using specific protocols. Sensor and relays are not able to communicate with the network protocols so RTUs used to communicate sensors and network interfaces. Information/Data presentation: The normal circuit networks have some indicators which can be visible to control but in the real-time SCADA system, there are thousands of sensors and alarm which are impossible to be handled simultaneously. The SCADA system uses the human-machine interface (HMI) to provide all of the information gathered from the various sensors. Monitoring/Control: The SCADA system uses different switches to operate each device and displays the status of the control area. Any part of the process can be turned ON/OFF from the control station using these switches. SCADA system is implemented to work automatically without human intervention but in critical situations, it is handled by manpower.

DATA ACQUISITION SYSTEM

A typical Data Acquisition System consists of individual sensors with the necessary signal conditioning, data conversion, data processing, multiplexing, data handling and associated transmission, storage and display systems Fig 3.5: Data Acquisition system

Data Acquisition System Block Diagram:

Single Channel Data Acquisition System:

A Single Channel Data Acquisition System consists of a signal conditioner followed by an analog to digital (A/D) converter, performing repetitive conversions at a free running, internally determined rate. The outputs are in digital code words including over range indication, polarity information and a status output to indicate when the output digits are valid.

1. It is slow and the BCD has to be changed into binary coding, if the output is to be processed by digital equipment.
2. While it is free running, the data from the A/D converter is transferred to the interface register at a rate determined by the DPM itself, rather than commands beginning from the external interface. Fig 3.7:

Computer Based Data Acquisition System:

Computer Based Data Acquisition System – If a large number of inputs are to be measured, some equipment is needed to measure them and display the results in a meaningful and operationally useful fashion. All this is possible with Data Acquisition System, which utilizes a computer driven visual display unit (CRT) as an operator aid. A screen display can be obtained within two seconds by pressing a button. Information may be displayed only when called up. The screen display can be designed in several ways, using a combination of graphical and numeric displays, so as to be of maximum utility to the operator. Data Acquisition System aids operate in the following manner.

• Display spatial as well as time variation.
• Display vital parameters grouped together logically and concisely, eliminating the need of looking at many scattered instruments.
• Display CRT graphic displays of plant sub-systems.
• Display short trends on a long- and short-term basis, as required.
• Analyze the data and present the highest priority problem first, and display operator guidance messages.
• Analyze the data and present the derived data; do performance calculations to depict the performance of several equipment and plants.
• Display alarms, indicating abnormal plant operating conditions on the
• Provide trending of analog variables on strip chart recorders, in the form of a histogram on the CRT, and provide dynamic updating of parameters.
• Produce a hard copy record of all plant operating events and various plant
• Provide a recording of the sequence of events, whenever an emergency occurs.

CHAPTER- 5

CERTIFICATE