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research paper focuses on the three main topics of Programmable Logic
Controller (PLC). The role it plays in automotive Industries environment, to
explain the advancement in how a PLC communicates with another device and to
describe the need for a safety PLC instead of a standard or general purpose

main Purpose of plc is dividing the huge task into pieces, organizes and gives
a sequential order of the output regards of the program in the real-time
application. PLC are designed in different shapes and sizes. The smaller PLC
like micrologic 1000, Micro logics 1400 are designed with fixed I/O module
mostly used to small project and plc trainer board. However, large PLCs are
used in big industries. It is more flexible to update the input-output (I/O)

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divided into four main components such as.

1.    The backplane and power supply.

2.    CPU (central processing unit)

3.    I/O (input/output)

4.    The Program section

Power supply converts the input power source to suitable and steady power to
the PLC.

  Processor(CPU) –  Is the brain of the PLC it controls all the
process functions.




•    Input module –  Read the incoming signal from the sensors,
limit switch.

•    Output module – Energize the contactors,
solenoids and motor controller (motor drive)

are two types of Input-output modules.

1.    Sinking ground connected to the load.

2.     Sourcing- voltage source is connected to
the load.


CPU also has four operating modes such as:

1.    Programming Mode – allow to download,
update or modify the program.

2.    Run Mode – Monitor the I/O and any
communication with another device.

3.    Stop Mode – Stop the sequence of the
program and it shut off the output.

4.    Reset Mode- Reset the program from
operation back to home position.


function, the PLC needs to complete few steps. These are plugging the PLC into
the power source, set the program selector switch of the PLC into program mode,
download the program finally set the program selector switch in to run mode.
Now the PLC is ready to initiate.

 There are two modes to start the sequence.

1.    Manual mode – To initiate the cycle it
requires pressing the start button.

2.     Auto mode – It initiates the cycle
automatically upon the feedback from the input part percent sensor. Once the
cycle starts the PLC keeps running unless something happened or part delayed.


determine the effectiveness of the PLC program (logic) need to analyze the scan
time which is the amount of time, that takes to complete the process from

presence of the part to the input and run the program to update the output. The
scan time is measured in a millisecond.


a programmable logic controller is a device used for automation of the typical
industrial electromechanical process, such as the control of machinery and
Robotics on the assembly lines and in harsh working environments. PLCs are used
in many machines. in many industries that minimizing the worker’s pressure
under Fast-paced environment and repetitive tasks by inters connected with
another machines and robots. It is designed to handle digital and analog inputs
and outputs and to store the program non-volatile (Static) memory. Once it
programmed it will stay for long period unless its damaged or reprogrammed.
“logic controller (PLC) is a special form of microprocessor-based controller
that uses a programmable memory to store instructions and to implement
functions such as logic, sequencing, timing, counting, and arithmetic to
control machines and processes and is designed to be operated by engineers with
perhaps a limited knowledge of computers and computing languages” (Bolton,
2009, p.16).





newest version of Programmable Logic Controller is more advance communication
port than the oldest one that’s only connected through

RS485, and RS232 to modify and update the program or for troubleshooting
purpose. It requires the presence of a technician through advancement, PLCs can
now communicate via the internet. “The most advanced

has an incorporated Ethernet port on the controller for two principal
operations. The first is controlling remote I/O on Ethernet-based conventions
like EtherNet/IP, Profinet, or Modbus/TCP. The second is to program and
additionally troubleshoot the interior program of the controller” (Reszka,
2011, para.2).


PLCs workers used to check each part manually in sorting and inspection line.
It was time-consuming and made it easy to expose the product to contamination.
Currently, the PLC takes over by communicating the vision system, inspect the
final product, decreases unnecessary contamination and handling problem,
decreasing human mistakes and increasing the quality and number of products.


today different manufacturers make different types of PLC. For example,
Siemens, Omron, Schneider, and Allen-Bradley are some of the

However, they have a different design and different programming approaches, but
all have the same purpose. All types of Programmable logic




essentially do the same thing inputting a set of instructions to implement
designated processes but a safety PLC is designed for the specific task hence,
minimizing workplace hazards. it has different criteria depending on

safety standards of the country. example China, Germany, and North America
standards. “A safety PLC is a dedicated controller specifically built and
certified to meet safety requirements, such as functional safety directives IEC
62061, ISO 13849-1 or IEC 61508 that defines Safety Integrity Level (SIL), or
the levels of risk reduction provided by some safety function” (Budimir, 2016,

a safety PLC is one of the requirements of safety standards it monitors safety
equipment such as a light curtain, area scanner, e-stop robot cell interlocks,
conveyor system, press machine, food, and beverage industries. That
continuously monitors and prevents workers from death, injuries and workplace hazards.  

closing, Programmable Logic Controller (PLC) is the brain of automation world
that monitors inputs from the sensors, limit switch processes based on the
program and energized the output and gives a sequential command to control the
machine. PLC is more flexible and compact in relation to the relay(contactor)
controlling system. It reduces human efforts by communicating and commanding
the robotic devices to complete manufacturing tasks, increases the number of
productions, minimizes the safety and workplace hazards and monitors the
quality of the product. On the other hand, it has disadvantages such as
unemployment rate Increases. However, the initial costs are higher since it
requires professionals to wire and program. In addition, it has significant advantages
in automation world: It is cost-effective, reduces waste material, Improves the
quality and productivity, it is also easy to program and to troubleshoot.
Overall PLC is reliable and repeatable. Making it the most important part of


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