Scenario
You are working for a local engineering company as a junior engineer dealing with the design and
implementation of different PLC applications. At the end of your training period your line manager has asked
you to write a report of maximum 40 pages (A4) to cover the answers to the following tasks:

TASK 1

P1:Understand the design and operational characteristics of a PLC system

a) Draw a block diagram showing in general terms the main units in a PLC system. Describe the
characteristics of each unit.
b) Explain the operation of the following input and output devices, stating the form of the signal being
sensed and the output:
I. Reed switch
II. Incremental shaft encoder
III. Photoelectric transmissive switch
IV. Diaphragm pressure switch.
c) A PLC must communicate with other devices. This is needed to link them to programming devices and to
other equipment. Investigate the different types of communication link used in PLC.
d) Describe the internal architecture and operational characteristics of the CPU of a typical PLC.
Cover in more depth the function and operation of the ALU unit within the CPU.

TASK 2

P2:Understand PLC information and communication techniques

Write about 1-3 pages on each of the following:

a) Explain what is meant by the terms combinational logic systems and sequential logic systems. How
each of these signal systems can be used in PLC. Describe the characteristics of each unit.
b) Describe the resolution and relationship between analogue inputs and word length of digital outputs.
c) Convert the decimal number 6481010 to Binary, Hexadecimal, and Octal numbers.
d) Compare the star, bus and ring forms of network and the methods used to avoid problems with messages.

TASK 3

P3: Be able to apply programmable logic programming techniques

Write about 1-3 pages on each of the following:

a) Identify the symbols associated with the drawing of ladder diagrams in PLC.

b) A panel of 8 people (1 president and seven members) has asked you to design a PLC ladder diagram for
a voting system. It should send ‘1’ to output Y430 if there is a majority agreement and ‘1’ to output Y431
if there is a majority disagreement. In the case of 50% split in the votes, the president’s vote will be
decisive. The votes were taken from inputs X400 to X407 as shown below:
c) Explain methods for testing and debugging the program written in task ‘c’ above.

TASK 4

P4: Understand alternative implementations of programmable control.

Write about 1-3 pages on each of the following:

a) Evaluate PICs PLCs, embedded controllers and Microprocessor systems.
b) Search the internet for a PLC simulator and then discuss the operation, functionality, advantages and
limitations of this simulator.

What to submit

– Your answers should be in a report format. Your report should not exceed 40 pages (A4). You may use
an Appendix for any additional information, which is not directly related to the body of your report. You may
visit the following IET website for a help in report writing format:

http://www.theiet.org/students/resources/final-year-project/writing-reports.cfm

– List of references (preferably in IEEE numeric style format). Wikipedia must not be used as a
reference. See the link below for details:

http://http-server.carleton.ca/~nartemev/IEEE_style.html

– 1 page (A4) self-evaluation of your assignment.
To achieve each learning outcome the learner must demonstrate the ability to:

Assessment Criteria for this Assignment

P1 Understand the design and operational characteristics of a PLC system
1.1 Evaluate the design characteristics of typical programmable logic devices
1.2 Describes different types of input and output device
1.3 Evaluate the different types of communication link used in programmable logic control systems
1.4 Describe the internal architecture and operational characteristics of the CPU of a typical
programmable logic device

P2 Understand PLC information and communication techniques
2.1 Evaluate the different forms of signal used in programmable logic control
2.2 Describe the resolution and relationship between analogue inputs and outputs and word length
2.3 Express numbers using different number systems
2.4 Describe typical protocols used in signal communication and evaluate networking methods and
networking standards

P3 Be able to apply programmable logic programming techniques
3.1 Identify elements associated with the preparation of a programmable logic controller program
3.2 Write programs using logic functions based on relay ladder logic
3.3 Evaluate the range and type of advanced functions of programmable logic controllers
3.4 Use and justify methods of testing and debugging hardware and software

P4 Understand alternative implementations of programmable control
4.1 Evaluate PICs and other programmable devices as programmable devices and embedded controllers
4.2 Compare the operation, functionality, advantages and limitations of PLC simulators.

Merit criteria assessed (include Pass criteria+):

M1: Identify and apply strategies to find appropriate solutions
• effective judgments have been made the content and the structure of the answers
• the answers demonstrate attention to detail and an effective approach to research

M2: Select/design and apply appropriate methods/techniques e.g.
• relevant theories and techniques have been applied to solve the problems and to answer the questions
• A wide range of sources of information has been used (at least 5).
• complex information has been effectively synthesised to answer the questions and solve the problems

M3: Present and communicate appropriate findings
• technical language has been coherently and accurately used in the context
• answers have been provided in the report format correctly laid out and presented for the intended
audience
• A list of references been appended.
• The list of references has been formatted according to an IEEE numeric format.

Distinction criteria assessed (include Merit criteria+):

D1: Use critical reflection to evaluate own work and justify valid conclusions
• conclusions have been arrived at through synthesis of ideas have been justified
• the answers demonstrate high attention to detail and an effective approach to research

D2: Take responsibility for managing and organising activities
• submission deadline has been met
• independence and autonomy have been demonstrated
• substantial investigation have been planned, managed and organised

D3: Demonstrate convergent/lateral/creative thinking e.g.
• problems have been effectively solved
• innovation and creative thought are evident in the students work
• effective self-evaluation has been taken place