What is a PLC?
PLC Stand for Programmable Logic Unit.
A PLC is an industrial digital computer that is specifically designed
to operate in harsh environment and conditions. These are made to
operate or automate a single process or machine function. This are
generally made to replace hardwired relays, timers and sequencers
used in rugged environment and unfavorable conditions for electrical equipment.
Components of PLC:
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| Components Of PLC |
PLCs are small industrial computer
units that are designed to perform a specific task or automate a
task. PLC consist of 3 major components that performs the complete
functioning of a PLC: A Processor, Power Supply and I/O Section.
A Power Supply:
The Power Supply Unit of an PLC converts the input source into the
required circuitry voltage. The power supply usually requires 110
Volts that is then converted into DC and transferred to the
respective components.
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| PLC Component- Power Supply |
A Processor:
The Processor or the brain of an PLC performs operations from the
inputs received from the Input Device. It is the main Logical unit
that organizes the all control activity by receiving the inputs,
perform the logical decisions and controlling the outputs.
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| Components of PLC- Processor |
I/O Section:
It as the body for the brain of an PLC. The Input Section receives
the information from real world input sources like, push buttons,
temperature switches, sensors, proximity switches, etc. The Output
Section than delivers the obtained result from the Processor in the
form of output Voltage required to control the loads such as, alarms,
lights, solenoids, etc.
How PLC Works?
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| How PLC Works |
The
Working of an PLC generally really on its components. The
power supply transfers regulated direct current power to the PLC. The
power supply will generally run off of 120 VAC or 24 VDC sources.
This means that depending on the PLC that is selected it will most
likely be able to be powered by a standard wall outlet.
The CPU is like the brain of the PLC.
This is where a microprocessor, memory chip, and other integrated
circuits come together perform logic control, monitoring, and
communications. The CPU of the PLC has different operating modes.
Programming mode allows programs/logic to be downloaded from a PC
source. Run mode is what the PLC is set to when functional operation
is desired. Since a PLC is a dedicated controller it will only
process a singular program over and over again. Once cycle through
the program is called a scan time and involves reading the inputs
from the other modules, executing logic based on these inputs and
then updating the outputs accordingly. The CPU memory stores the
program, statuses of I/O, and can store values if necessary. There
are many different types of I/O configuration for a PLC.
Input devices can be either digital or
analog. Digital inputs are specific values or on/off, analog inputs
on the other hand need to have their voltage or current converted to
a digital equivalent number before they can be processed. Outputs can
also be both digital and analog. A digital output would turn
something on or off. An analog output would be converted back to its
voltage or current representation which can then be used to drive
mass flow controllers, pressure regulators, position controls, and
more.
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