1. 3442 Industrial Instruments 2 Chapter 8 Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
Princess Sumaya Univ. Electronic Engineering Dept.
3442 Industrial Instruments 2 Chapter 8 Discrete-State Process Control
Dr. Bassam Kahhaleh
Dr. Bassam Kahhaleh

2. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
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

3. 8: Discrete-State Process Control
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Industrial Instruments 2
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

4. 8: Discrete-State Process Control
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Industrial Instruments 2
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

5. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
Discrete-State Variables
Continuous Control

6. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Discrete-State Variables
Continuous Control
Discrete Control

7. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Discrete-State Variables
Continuous Control
Discrete Control
Composite Discrete/Continuous Control

8. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
Process Specifications
Process Objectives
Process Hardware
Input Devices
Limit Switches
Comparators
Push Buttons
Output Devices
Lights
Motors
Solenoids

9. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
Event Sequence Description
Narrative Statements
Flowcharts
Binary-State 00 01 1X
X / 0
1 / 1
0 / 0
X / 1

10. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
Event Sequence Description
Flowchart Example

11. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Event Sequence Description
Flowchart Example

12. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Event Sequence Description
Binary-State Example
Fill the tank to level A from valve A.
Fill the tank to level B from valve B.
Start the timer, heat, and stir for 5 minutes.
Open output valve C until the empty switch engages.

13. 8: Discrete-State Process Control
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Industrial Instruments 2
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

14. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Event Sequence Description
Binary-State Example
State: LA LB LE TU VA VB VC TM S H

15. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Control Relays (Relay Sequencer)

16. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram

17. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example

18. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example

19. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example

20. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example

21. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example
When the START button is pushed, the platform is driven to the down position.
When the STOP button is pushed, the platform is halted at whatever position it occupies at that time.
When the UP button is pushed, the platform, if it is not in downward motion, is driven to the up position.
When the DOWN button is pushed, the platform, if it is not in upward motion, is driven to the down position.

22. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example
Start
Stop

23. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example
START
STOP
Power

24. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example
START
↓ Motor
STOP
Power

25. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example
START
↓ Motor UP
↑ Motor
STOP
Power
Down

26. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Relay Controllers & Ladder Diagrams
Ladder Diagram Example CR CR

27. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Hardwired Programming
Relay Sequencers
Programmable Logic Controllers (PLCs)
Processor
Input Modules
Output Modules

28. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Programmable Logic Controllers (PLCs)
Input Module

29. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
8: Discrete-State Process Control
Programmable Logic Controllers (PLCs)
Output Module

30. 8: Discrete-State Process Control
Princess Sumaya University
Industrial Instruments 2
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:
The button turns the light OFF.
With relay logic the button turns the light ON.
With a PLC program the button turns the light ON

31. 8: Discrete-State Process Control
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Industrial Instruments 2
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.

32. 8: Discrete-State Process Control
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Industrial Instruments 2
8: Discrete-State Process Control
End of Chapter 8