Programmable Logic Controller: Communication Mediums and Standards

This report discusses the various communication mediums and standards applied to modern programmable controller systems, including twisted pair, coaxial cables, fiber optics, and protocols such as RS-232, RS-422, IEEE 488, and EIA-485. It also includes a diagram for establishing connections with PLCs and a comparison between RS-232 and IEEE-488. The subject is Programmable Logic Controller, and the course code, course name, and college/university are not mentioned.

Running head: PROGRAMMABLE LOGIC CONTROLLER
Programmable Logic Controller
[Name of the Student]
[Name of the University]
[Author note]

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Table of Contents
Introduction:....................................................................................................................................2
Discussion:.......................................................................................................................................2
1. Types of communication medium:..........................................................................................2
1.1. Twisted pair:.....................................................................................................................2
1.2. Coaxial cables:..................................................................................................................2
1.3. Fiber Optics:.....................................................................................................................3
2. Protocols and standards:..........................................................................................................3
2.1. Protocols and Standards applied to Modern Programmable Controller System:.................3
2.1.1. RS 232:..........................................................................................................................3
2.1.2. RS 422:..........................................................................................................................4
2.1.3. IEEE 488:.......................................................................................................................4
2.1.4. EIA-485:........................................................................................................................4
2.2. Diagram used for establishing connection with PLC...........................................................5
3. Comparison of RS-232 vs IEEE-488:......................................................................................6
Conclusion.......................................................................................................................................7

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Introduction:
PLC or Programmable Logic Controller or Programmable controller refers to the
industrial digital computer that has been ruggedized for the purpose of controlling the processes
involved in the manufacturing and this might include the robotic devices or the assembly lines or
any type of activities that requires a high reliability control or ease of programming or the
process free diagnosis (Yordanov et al. 2012). This report is going to discuss about the various
communication mediums which includes the Twisted Pair, Coaxial cable, and fibre Optic. Along
with this the report also discusses about the protocol and the standard that is applied to the
modern programmable controller system, the network diagram.
Discussion:
1. Types of communication medium:
1.1. Twisted pair:
Twisted pair cables are the wire which consist of a single circuit which are twisted
together to cancel out the electromagnetic interference from any type of external source
(Eltamaly and Farh 2013). The common example of the twisted pair is the copper wire which is
used for connecting the telephones to the network. The two copper wires are insulated so that
more than one twisted cables can be placed inside an outer insulted layer (Nawaz and Bourrie
2012). The twisted pairs are provided with different colours so as to identify them when they are
packed in the multiple pairs.

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1.2. Coaxial cables:
This type of cables is widely used for the purpose of connecting computers or PLC’s with
different systems like the Ethernet and the LAN. This type of cable consists of an inner
conductor which is surrounded by one concentric conductor which is made up of copper mesh
and this two layers are separated by a layer of insulation (Al Nabulsi and Dhaouadi 2012). The
outer layer of this cables are mainly grounded so that they can carry information at a greater
distance.
1.3. Fiber Optics:
Fiber optic cables are those types of cables which are basically made up of thin glass
strands. The light travels over the fibers at great distances without even losing its strength. The
information carried through optic fibres are much faster than any other conventional copper
wires and are not subjected to any type of electromagnetic interference or retransmitted signal
(Novoselov et al. 2016). Many strands in the optic fibers are bundled up so as to provide many
more channels. Along with this Fiber Optics also provides data security and this cables are also
non-conductive in nature, the hazard due to any type of spark is also eliminated.
2. Protocols and standards:
2.1. Protocols and Standards applied to Modern Programmable Controller
System:
There are various standards applied to the Modern Programmable controller system and
this includes the following:

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2.1.1. RS 232:
This standard is mainly for the interface and the protocol that is used for the purpose of
linking the computers to the electronic equipment’s of the industry (Guerriero et al. 2013). After
going through various updates the recent one is the RC232C.
2.1.2. RS 422:
This system is almost similar to that of the RS 232 but the only difference is that this type
of standard is preferred in transmission over long cables.
2.1.3. IEEE 488:
The main standard used in the parallel transmission is the IEEE 488.
2.1.4. EIA-485:
This standard was formerly known as the RS-485 or RS485 and is a standard used for the
serial communication of the 2 wires.

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2.2. Diagram used for establishing connection with PLC
Fig 1
Source: (Created by Author)

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Standard interface used for communication is IEEE-488 and it is also known as General Purpose
Instrument Bus (GBIP) (Papadopoulos, Chrysochos and Papagiannis 2013). The advantages and
disadvantage are described below:
Advantage
 GPIB is a simple interface
 GBIP has ports for interface which is widely available on the various test and
equipment’s for measurement.
 GPIB cables are considered to be very rugged and provide robust connectors.
 By making use of GPIB interface single controller can be analysed or checked.
 It also provides control over various T & M equipment’s or devices.
Disadvantage
 The connectors used in GPIB are considered to be bulky.
 Interface generally carries low bandwidth of data.
 GPIB interface is generally used for data communication at low speed whereas modern or
recent interface generally used for communication at high speed rate.
 Current device has reduced its usage and it is expected that in coming years of the future
it can become isolated.
3. Comparison of RS-232 versus IEEE-488:
RS-232 communication is considered to be most popular or well-known method of PLC
which is used for external communication (Xia, Gupta and Antsaklis 2013). This particular
communication interface is considered to operate under SCADA mode of application. Other

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standards are like RS422 and RS423 which are similar to this RS232 whereas they provide much
higher rates of transmission of data along with many longer cables.
Conclusion
From the above discussion it can be concluded that this report is all about different kinds
of communication media which is selected for a particular PLC, comparison between modern
PLC and a particular network has been described in details. Different type of communication
medium like twisted pair, coaxial cables, fiber optics, various protocol and standard has been
described in details in the above pages of the report. Four most common type of protocol that is
RS 232, RS422, IEEE 488, EIA-485 has been described in details in this report. A proper
diagram has been provided which is used for establishing connection various PLC has been
describe in this report briefly. Advantages and Disadvantages of IEEE-488 has been described in
details in this report. A proper discussion has been provided in the above pages regarding the two
standards that is RS-232 and IEEE-488.

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