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3442 Industrial Instruments 2 Chapter 8 Discrete-State Process Control Dr. Bassam Kahhaleh Princess Sumaya Univ. Electronic Engineering Dept.

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Princess Sumaya University Industrial Instruments 22 / 32 8: Discrete-State Process Control Definitions The discrete state of the process at any moment is the set of all input and output values. An event in the system is defined by a particular state of the system, i.e. particular values of inputs and outputs. A discrete-state process control is a particular sequence of events through which the process accomplishes some objective

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Princess Sumaya University Industrial Instruments 23 / 32 8: Discrete-State Process Control Example Frost-free refrigerator/freezer Discrete-state I/P Door open/closed Cooler temp. high/low Freezer temp. high/low Power switch on/off Frost detector on/off Frost eliminator timer out/not out

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Princess Sumaya University Industrial Instruments 24 / 32 8: Discrete-State Process Control Example Frost-free refrigerator/freezer Discrete-state O/P Light on/off Compressor on/off Timer on/off Heater on/off Baffle open/closed

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Princess Sumaya University Industrial Instruments 25 / 32 8: Discrete-State Process Control Discrete-State Variables Continuous Control

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Princess Sumaya University Industrial Instruments 26 / 32 8: Discrete-State Process Control Discrete-State Variables Continuous Control Discrete Control

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Princess Sumaya University Industrial Instruments 27 / 32 8: Discrete-State Process Control Discrete-State Variables Continuous Control Discrete Control Composite Discrete/Continuous Control

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Princess Sumaya University Industrial Instruments 28 / 32 8: Discrete-State Process Control Process Specifications Process Objectives Process Hardware Input Devices Input Devices Limit SwitchesLimit Switches ComparatorsComparators Push ButtonsPush Buttons Output Devices Output Devices LightsLights MotorsMotors SolenoidsSolenoids

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Princess Sumaya University Industrial Instruments 29 / 32 8: Discrete-State Process Control Event Sequence Description Narrative Statements Flowcharts Binary-State X X / 0 1 / 1 0 / 0 X / 1

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Princess Sumaya University Industrial Instruments 210 / 32 8: Discrete-State Process Control Event Sequence Description Flowchart Example

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Princess Sumaya University Industrial Instruments 211 / 32 8: Discrete-State Process Control Event Sequence Description Flowchart Example

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Princess Sumaya University Industrial Instruments 212 / 32 8: Discrete-State Process Control Event Sequence Description Binary-State Example 1. Fill the tank to level A from valve A. 2. Fill the tank to level B from valve B. 3. Start the timer, heat, and stir for 5 minutes. 4. Open output valve C until the empty switch engages.

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Princess Sumaya University Industrial Instruments 213 / 32 8: Discrete-State Process Control Event Sequence Description Binary-State Example I/P Variables LA LB LE TU O/P Variables VA VB VC TM S H

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Princess Sumaya University Industrial Instruments 214 / 32 8: Discrete-State Process Control Event Sequence Description Binary-State Example State: LA LB LE TU VA VB VC TM S H

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Princess Sumaya University Industrial Instruments 215 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Control Relays (Relay Sequencer)

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Princess Sumaya University Industrial Instruments 216 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram

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Princess Sumaya University Industrial Instruments 217 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example

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Princess Sumaya University Industrial Instruments 218 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example

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Princess Sumaya University Industrial Instruments 219 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example

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Princess Sumaya University Industrial Instruments 220 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example

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Princess Sumaya University Industrial Instruments 221 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example 1.When the START button is pushed, the platform is driven to the down position. 2.When the STOP button is pushed, the platform is halted at whatever position it occupies at that time. 3.When the UP button is pushed, the platform, if it is not in downward motion, is driven to the up position. 4.When the DOWN button is pushed, the platform, if it is not in upward motion, is driven to the down position.

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Princess Sumaya University Industrial Instruments 222 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example Start Stop

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Princess Sumaya University Industrial Instruments 223 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example START STOP Power

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Princess Sumaya University Industrial Instruments 224 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example START STOP Power ↓ Motor

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Princess Sumaya University Industrial Instruments 225 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example Power Down STOP START ↑ Motor ↓ Motor UP

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Princess Sumaya University Industrial Instruments 226 / 32 8: Discrete-State Process Control Relay Controllers & Ladder Diagrams Ladder Diagram Example CR

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Princess Sumaya University Industrial Instruments 227 / 32 8: Discrete-State Process Control Hardwired Programming Relay Sequencers Programmable Logic Controllers (PLCs) Processor Input Modules Output Modules

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Princess Sumaya University Industrial Instruments 228 / 32 8: Discrete-State Process Control Programmable Logic Controllers (PLCs) Input Module

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Princess Sumaya University Industrial Instruments 229 / 32 8: Discrete-State Process Control Programmable Logic Controllers (PLCs) Output Module

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Princess Sumaya University Industrial Instruments 230 / 32 8: Discrete-State Process Control Programmable Logic Controllers (PLCs) Logic Programming Using a NC switch to turn off a light with relay logic and with PLC programming: a)The button turns the light OFF. b)With relay logic the button turns the light ON. c)With a PLC program the button turns the light ON

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Princess Sumaya University Industrial Instruments 231 / 32 8: Discrete-State Process Control Programmable Logic Controllers (PLCs) Logic Programming NO switches are considered INACTIVE when they are read as open circuit, and ACTIVE when they are read as closed circuit. In the ladder diagram, 01 must be ACTIVE while 03 must be INACTIVE to turn 08 ON.

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Princess Sumaya University Industrial Instruments 232 / 32 8: Discrete-State Process Control End of Chapter 8

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