The Components of a PLC
Component
Solutions to control problems realize technically with PLC applications and may vary in their complexity. However, the following building blocks are always necessary:
Hardware:
By hardware, we understand the electronic modules, through which all functions of the installation or machine to be controlled are addressed and actuated in the logical sequence.
Software:
By software we mean the programs in which logic operations and the related triggering of components within the installation or machine are precisely specified. The software is filed in particular hardware memory and can be modified if required. The control sequence changes with the new program. It is not necessary to modify the hardware.
Sensors (Sensors):
By attaching these components directly to the machine or installation to be controlled, information regarding the current status of these devices can be transmitted to the PLC. Sensors are, e.g., limit or proximately switches.
Actors (Actuators):
These are the components fitted directly to the machine or installation to be controlled, which can be used to change status via the PLC. In other words, sequences can be influenced, or changes in status can be announced. Examples of Actuators are buzzers and solenoid valves.
Programmer:
The developer is used to create the software and to transfer it to the PLC Memory. In most cases, it can also be used for testing software Sensorics and Actorics.
Hardware
The most important components of the PLC device is the central control unit (CCU) which corresponds to a computer in structure. The processes taking place in the central control unit are designed processors (processing).
The data processed and stored in the CCU are in the form of binary signals, each as a rule composed of a single bit (with status zero or one).
The input and output modules make the connection between the central control unit and the actuators/sensors. Each of these modules contains a fixed number of inputs and outputs which can assume the binary values, Zero and one. A critical component of the central control unit is the flag memory. Flag is one-bit memories, through which the PLC can “Note” the status of binary signals.
Software
PLC programs have a concrete structure, determined in the Central Control Unit. They are created by the programmer from source programs, in principle, the programmer can create these programs by four different methods:
As a statement list program (STL)
As a ladder diagram (LAD)
Function Chart or Control System Flow Chart (CSF)
PLC Visual Scripts
Sensors
Sensors are signal generators, which can be used by the PLC to integrate the status of the installation or machine to be controlled. As the PLC works “Electrically,” the sensors must convert non-electric signals into electric ones so that they can be understood by the input module. Examples of sensors are:
I) Limit Switches
Normally closed contacts, normally open contacts or changeover contacts.
II) Initiators
Contacting and contactless switches, which emit one or zero signal when approached by an object, inductive generators react to metal parts, capacitive generators also to other materials.
III) Light Barriers
Contacting and contactless switches, which emit one or zero signal when an optical connection is interrupted.
IV) Temperature Sensors
Contacting and contactless switches emitting one or zero signal on attainment of a set temperature value.
Actors
Actors are executive elements used to amplify binary signals from the output modules to create switching signals or to convert them into signals of another energy type.
The distinction is made between electric, electro hydraulic and electro pneumatic actuators. They can be used to create switching processes and linear or rotary movements. Examples of actuators are:
Alarms
Lamps, Buzzers, Bell
Pneumatic Cylinders (with value systems)
Single and double acting cylinders, cylinders with through rod, tandem cylinders, multi positions cylinders.
Electro Motors
DC motors, stepping motors, synchronous, AC motors, rotating vane motors.
Hydraulic actuators (with value system)
Single or double acting cylinders, flow control valves, hydraulic motors.
Electro Hydraulic Motors
Stepper motors, servo drives etc.
Programmer
The developer is used to write and correct programs to translate them into the PLC machine code to transmit them to the PLC and to test them. It can be just like a simple or unique personal computer.
Personal Computer
In the past, this was mainly carried out using specialized tools, tailor made for individual manufacturers control system. Today conventional personal computers are increasingly being used as programming tools loaded for the task with programming software specific to the control system involved.
Programming System
Programming Systems based on the personal computer mostly offer several methods of programming, i.e., the programmer creates a source program graphically or in plain text, which the programming system translates into machine code, understood by the PLC being used. If the personal computer processes a data interface suitable for the PLC, programs can be transmitted directly into the program memory of the PLC.
To gain a better overall view and for the purpose of programming methods documentation, it is possible to print out the programs created.
Component
Solutions to control problems realize technically with PLC applications and may vary in their complexity. However, the following building blocks are always necessary:
Hardware:
By hardware, we understand the electronic modules, through which all functions of the installation or machine to be controlled are addressed and actuated in the logical sequence.
Software:
By software we mean the programs in which logic operations and the related triggering of components within the installation or machine are precisely specified. The software is filed in particular hardware memory and can be modified if required. The control sequence changes with the new program. It is not necessary to modify the hardware.
Sensors (Sensors):
By attaching these components directly to the machine or installation to be controlled, information regarding the current status of these devices can be transmitted to the PLC. Sensors are, e.g., limit or proximately switches.
Actors (Actuators):
These are the components fitted directly to the machine or installation to be controlled, which can be used to change status via the PLC. In other words, sequences can be influenced, or changes in status can be announced. Examples of Actuators are buzzers and solenoid valves.
Programmer:
The developer is used to create the software and to transfer it to the PLC Memory. In most cases, it can also be used for testing software Sensorics and Actorics.
Hardware
The most important components of the PLC device is the central control unit (CCU) which corresponds to a computer in structure. The processes taking place in the central control unit are designed processors (processing).
The data processed and stored in the CCU are in the form of binary signals, each as a rule composed of a single bit (with status zero or one).
The input and output modules make the connection between the central control unit and the actuators/sensors. Each of these modules contains a fixed number of inputs and outputs which can assume the binary values, Zero and one. A critical component of the central control unit is the flag memory. Flag is one-bit memories, through which the PLC can “Note” the status of binary signals.
Software
PLC programs have a concrete structure, determined in the Central Control Unit. They are created by the programmer from source programs, in principle, the programmer can create these programs by four different methods:
As a statement list program (STL)
As a ladder diagram (LAD)
Function Chart or Control System Flow Chart (CSF)
PLC Visual Scripts
Sensors
Sensors are signal generators, which can be used by the PLC to integrate the status of the installation or machine to be controlled. As the PLC works “Electrically,” the sensors must convert non-electric signals into electric ones so that they can be understood by the input module. Examples of sensors are:
I) Limit Switches
Normally closed contacts, normally open contacts or changeover contacts.
II) Initiators
Contacting and contactless switches, which emit one or zero signal when approached by an object, inductive generators react to metal parts, capacitive generators also to other materials.
III) Light Barriers
Contacting and contactless switches, which emit one or zero signal when an optical connection is interrupted.
IV) Temperature Sensors
Contacting and contactless switches emitting one or zero signal on attainment of a set temperature value.
Actors
Actors are executive elements used to amplify binary signals from the output modules to create switching signals or to convert them into signals of another energy type.
The distinction is made between electric, electro hydraulic and electro pneumatic actuators. They can be used to create switching processes and linear or rotary movements. Examples of actuators are:
Alarms
Lamps, Buzzers, Bell
Pneumatic Cylinders (with value systems)
Single and double acting cylinders, cylinders with through rod, tandem cylinders, multi positions cylinders.
Electro Motors
DC motors, stepping motors, synchronous, AC motors, rotating vane motors.
Hydraulic actuators (with value system)
Single or double acting cylinders, flow control valves, hydraulic motors.
Electro Hydraulic Motors
Stepper motors, servo drives etc.
Programmer
The developer is used to write and correct programs to translate them into the PLC machine code to transmit them to the PLC and to test them. It can be just like a simple or unique personal computer.
Personal Computer
In the past, this was mainly carried out using specialized tools, tailor made for individual manufacturers control system. Today conventional personal computers are increasingly being used as programming tools loaded for the task with programming software specific to the control system involved.
Programming System
Programming Systems based on the personal computer mostly offer several methods of programming, i.e., the programmer creates a source program graphically or in plain text, which the programming system translates into machine code, understood by the PLC being used. If the personal computer processes a data interface suitable for the PLC, programs can be transmitted directly into the program memory of the PLC.
To gain a better overall view and for the purpose of programming methods documentation, it is possible to print out the programs created.
