PLC Flashcards
digitally operating electronic apparatus which uses a programmable memory for the internal storage of instructions by implementing specific functions, such as logic, sequencing, timing, counting, and arithmetic to control through digital or analog I/O modules various types of machines or processes.“
Programmable Logic Controller (PLC)
also known as the conventional relay logic replacer
PLC
an electronic apparatus capable of storing logic and arithmetic operation used to control machines and processes.
Programmable Logic Controller
PLC LEADING BRANDS
American: Allen Bradlley
European: Siemens
Asia: Omron and Mitsubishi
is built by several modules within a single case. Therefore I/O capabilities are decided by the manufacturer, but not by user.
Compact PLC
In compact type of PLC the maximum expansion possible is _
expansion.
3
A compact type of PLC must be:
- Suitable for stand alone
- Fix number I/O’s module
-Designed for simple application
is built by several components that are plugged into a common rack or bus with extendable
I/O capabilities.
Modular PLC
It is a type of PLC used for more complex and sophisticated control
- Flexible and versatile
- Huge I/O capabilities
- Suitable for centralized control systems
Modular PLC
From Sensors:
Push buttons, contacts, input switches, etc.
Major Components of PLC
From input > Processor +power supply +programming device > output module
Output module
Solenoids, Contacts, Alarms, etc.
Consist of Input modules and Output Modules
Input / Output (I/O) Section
The most common type of I/O Interface module is
Discrete I/O Module
It makes decisions and executes control
instructions based on the input signal
Processor (CPU)
Its function is to store and run the PLC software
programs
Processor (CPU)
It monitors the inputs and makes decisions in a PLC
Processor (CPU)
It is the brain of the PLC
Processor (CPU)
system that converts AC from the wall outlet
into the DC required by electronics circuit.
Power Supply
Supplies DC power to other modules that plug into
the rack
Power Supply
In large PLC system this power supply does not
normally supply power to the field devices
In small and micro PLC systems the power supply
is also used to power field devices.
Power Supply
Programming Device
Personal Computer is the most commonly used programming device
allows user to create, edit , document, store, and troubleshoot programs
software
communicates with PLC via serial or parallel data communications link
Personal Computer
PLC PROGRAMMING LANGUAGE
-Ladder logic (most common type of programming)
-Instruction list (IL)
- Sequential Function Chart (SFC)
-Structured Text (ST) or
-Function Block Diagram (FBD)
Siemens version:
-Structured Control -Language (SCL) = (ST)
-Statement List (STL) = (IL)
the most popular language today, especially in the US. It is based on the graphical representation of Relay Ladder Logic. Most current PLCs, whether compliant or not compliant with IEC61131-3, will support this
LADDER LOGIC
This is like a version of ladder language but intextform. It has the same structure as assembly language.
Instruction List( Siemens is called STL Statement List )
This language is less used in practice than LAD
Instruction List( Siemens is called STL )
Provide another view of a set of instructions. Each function has a name to designate its specific task. Functions are indicated by a rectangle. Inputs are shown on the left- hand side(EN or enable in) and outputs are shown on the right-hand side(ENO or enable out).
Function Block Diagram
This is a very powerful high-level language for PLC, derived from thePascal / C language.This is a language that is being increasingly used by engineers because it saves time
It can be used to define complex function blocks, which can be used in other languages. As a high-level language, _____ is very intuitive and easy to understand.
Structured Text (Structured Control Logic for Siemens)
This is a powerful graphical programming style to describe the sequential states of a control program. However, it is a bit difficult to learn and time consuming to program, so it is the least used language of the 5 languages according toIEC61131-3.
It is mainly used in programming control problems in sequential cycles
Sequential Function Chart (CFC for Siemens)
