Electrical and Electronic Engineering: PLC Programming Solution

This document presents a comprehensive solution to a PLC programming assignment, addressing key concepts within the field of electrical and electronic engineering. The assignment covers topics such as ladder diagram programming and the structure of programmable logic controllers (PLCs). The solution includes detailed explanations and diagrams for various scenarios, including input/output addressing, relay logic, and the operation of different components within a PLC system. The assignment also explores the CPU's role, the memory cycle, and the functionality of image tables. Furthermore, the solution provides a practical example of motor control using star-delta connections. The document concludes with a bibliography of relevant sources, offering a valuable resource for students studying PLC programming and control systems. This solution is designed to assist students in understanding and applying the principles of PLC programming to real-world applications. This assignment is published on Desklib, a platform that provides AI-based study tools for students.

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PLC Programming:
Electrical and Electronic Engineering Control
Student Name
Course Title: Course Name
Name of Professor
Date

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QUESTION 1
(a)

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b (i)

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(ii)
NO LABEL
INPUT/
OUTPUT
ADDRES
S
1 Push button P1 INPUT X001
2 Push button P2 INPUT X002
3 Push button P3 INPUT X003
4 Switch R1/2 INPUT X004
5 Switch R2/1 INPUT X005
6 Switch R3/2 INPUT X006
7 Switch SW1 INPUT X007
8 Switch R1/1 INPUT X008
9 Switch R2/1 INPUT X009
10 Switch R3/1 INPUT X010
11 Relay R1 OUTPUT Y001
12 Relay R2 OUTPUT Y002
13 Relay R3 OUTPUT Y003
14 Indicator IND1 OUTPUT Y004
15 Indicator IND2 OUTPUT Y005
16 Indicator IND3 OUTPUT Y006
17 Bell OUTPUT Y007
(iii)
 PLCs have faster response time
 PLCs are easier to troubleshoot
 PLCs offer lower cost
 More flexibility
 Increased reliability

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QUESTION 2
(i)
(ii)

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NO LABEL
INPUT/
OUTPUT ADDRESS
1 Key Switch INPUT X001
2 NO Push button P1 INPUT X002
3 Switch R1/1 INPUT X003
4 NC Push button P2 INPUT X004
5 Switch R1/2 INPUT X005
6 Switch R1/3 INPUT X006
7 NC Switch R3/2 INPUT X007
8 NO Push button P3 INPUT X008
9 Travel limit 1 INPUT X009
10 Switch R2/1 INPUT X010
11 Switch R1/4 INPUT X011
12 Switch R2/2 INPUT X012
13 NO Push button P4 INPUT X013
14 Travel limit 2 INPUT X014
15 Switch R3/1 INPUT X015
16 Relay R1 OUTPUT Y001
17 Indicator IND1 OUTPUT Y002
14 Forward relay R2 OUTPUT Y003
15 Indicator IND2 OUTPUT Y004
16 Reverse relay R3 OUTPUT Y005
17 Indicator IND3 OUTPUT Y006
(iii)
a) Rung 1 is for safety control. By operating the normally closed push button P2, in case of a fault,
the industrial process is stopped.
b) When IND2 is illuminated, switch R1/3 is closed and so is R3/2. Push button P3 is activated and
R2 energized. This causes R2/1 to also close.
c) IND3 remains ON. This is because the relay coil R3 remains energized despite P3 being operated.
QUESTION 3

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(i)
CPU - communicates and interprets the input signals and carries out control actions according to
program stored in memory
Power Supply - converts the mains ac voltage to low dc voltage for use by the electronic components
Input/output Interfaces – where the processor receives information from external devices and
communicates to the external devices
Memory- where program and data is stored
Keyboard and Display device – used to enter the program into the memory of the processor
(ii)

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The cycle begins by MAR storing the memory addresses of the data to be fetched by the
processor. The data stored in 1661 location is then fetched and executed on by the instructions
stored in the program memory. The process is then repeated till the instruction stored in the
1663 location is fetched, decoded and executed.
Contents after completion of the cycle
The PC and AS will be incremented by 3. The registers and accumulator will be BC – since BC is
the last instruction to be executed.
QUESTION 4

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(a) When the start button is pressed, the centrifugal switch closes the contactor C2-1
thereby completing the star circuit. As soon as it gets to speed, the centrifugal switch
opens and the delta contactor is closed. The motor thus runs in delta connection. Main
contactor remains always connected.
(b)
QUESTION 5

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 Image table is a memory location dedicated for the input/output bit status.
 It is characterized by a scan time.
 Once a PLC is powered, the CPU scans the input then transfers its data contents to the
input image table. The output data is transferred from the output image table to the
output module.
 The program is then scanned and a bit 1 output written into the output image table if
the conditions are met. The output device is thus energized. The vice-versa takes place if
the conditions are not met.
Bibliography

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Bolton, W. "Programmable Logic Controllers." Programmable Logic Controllers, 2009, 1-19.
doi:10.1016/b978-1-85617-751-1.00001-x.
Bolton, William. Programmable Logic Controllers. Amsterdam: Elsevier, 2011.
Hanssen, Dag H. Programmable Logic Controllers: A Practical Approach to IEC 61131-3
Using CoDeSys. Hoboken: John Wiley & Sons, 2015.
Kulkarni, Onkar R., and R. A. Metri. "Automatic Toll Monitoring System using PLC-SCADA
programming." 2019 9th International Conference on Cloud Computing, Data Science
& Engineering (Confluence), 2019. doi:10.1109/confluence.2019.8776940.
"Ladder Logic in Action." Library.Automationdirect.com. Last modified October 17, 2019.
https://library.automationdirect.com/ladder-logic-action/.
"Ladder Logic Tutorial - Part 2: Building Logic." PLC Academy. Last modified February 21,
2019. https://www.plcacademy.com/ladder-logic-tutorial-part-2/.
Lin, Jonathon. Programmable Logic Controllers. Industrial Press, 2016.
Stouffer, Keith, Joe Falco, and Karen Scarfone. "Guide to Industrial Control Systems (ICS)
Security - Supervisory Control and Data Acquisition (SCADA) systems, Distributed
Control Systems (DCS), and other control system configurations such as Programmable
Logic Controllers (PLC)." 2011. doi:10.6028/nist.sp.800.82.