2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
At the origins of industrial automation were relay-contact control circuits for production functions. Such devices had a specific unpleasant sound of operation. The logic of work was fixed, and at the slightest deviation from the set algorithm of actions, the entire editing chain had to be radically changed.
With the development of technology in this area, processors have evolved greatly. This served as a catalyst for the creation of industrial process control systems based on industrial PLC controllers.
The first such programmable controllers were used in the United States. They served to organize automation in the conveyor assembly line in the manufacture of automobiles. The company that applied this technology was Modicon in 1968.
Device Description
PLC Programmable Logic Controllers is a machine controlled by a program with multiple inputs that are connected to the object using control sensors. The outputs are connected to command execution devices. In the design of the controller, an important constituent element ismicroprocessor. Its task is to collect information, transform and store it for the possibility of further development of control commands. One of the main advantages of a programmable controller is that it functions in real time!
Previously, relay controllers had bulky overall dimensions, performed the simplest switching operations. Their logical structure was monolithic, not changeable. The PLC controllers that replaced them were distinguished by their compact size, the control algorithm rose to a new, complex level of performance. The process of free programming has emerged.
Logic controller capabilities
When developing the PLC, the creators pursued the goal of being able to control logic functions in a serial circuit. At present, programmable controllers can not only perform logical operations, but also process digital signals, control various drives, perform adjustments, and have acquired electronic operator control skills.
At the moment, devices are widely used in various fields. For example, the PLC 100 controller is designed to create automated control systems for production equipment in industry, agriculture, and housing and communal services. Also, PLCs are used in the energy sector, in the field of communications, and in the chemical industry. The devices have found their niche in the production and transportation of oil and gas, in security systems,take part in the automation of storage facilities, food production, transportation, construction and many other sectors of human life.
Distinguishing Features
PLC controllers share some of the characteristics of electronic devices used in industry.
Firstly, programmable logic devices differ from parallel microcontrollers in their use in the field of automated processes in enterprises with an industrial bias.
Secondly, programmable controllers are aimed at interacting with devices through the advanced input of sensor signals and their output to actuators, unlike computers, which are adapted to making decisions through operator control.
Third, what distinguishes PLC controllers from embedded systems is their self-sufficiency in terms of their manufacture as an independent product, separate from the equipment controlled by it.
PLC Advantages
Also, the PLC programmable controller is characterized by ease of contact with the user. This is expressed in the actions of programming the PLC itself according to the circuit diagram, according to logical equations and using the basic algorithmic language.
The device is adapted for operation in negative production conditions, using optical electronic isolation of inputs / outputs from external electrical circuits. This became possible due to the adaptabilitycontroller to a wider range of operating conditions.
The advantages of programmable controllers include software mobility due to the unification of programming languages, wide functionality, rapid change of modular units, real-time operating mode, repairability and system integration.
Select device
When choosing a PLC, they are guided by such basic criteria as compliance with the technical capabilities of the task and, of course, the cost of the device.
A huge number of manufacturers are engaged in the release of these controllers. The list includes both foreign firms and domestic ones. For example, the Russian firm "Oven" offers a PLC 150 controller that meets all the necessary specifications. Also in this list are the manufacturing companies "Elemer", "Emikon", "Tekon", "Fastwell", NIL AP and many others.
Famous foreign manufacturers are Siemens, Mitsubishi, ABB, Omron, Schneider Electric and others.
Over time, there has been a trend in the evolution of programmable logic controllers. They are losing size, expanding the set of functionalities, adding the number of compatible networks and interface shells, the idea of "open systems" is becoming widespread, the programming language is being standardized, and the realized price is being reduced.
It is worth noting that profitabledistinctive features of programmable controllers from personal computers in the form of appointments and the presence of a technological programming code.
Working principle
The operation of PLC controllers is slightly different from standard microprocessor-based instruments. The software shell of these logic controllers includes two parts. Like a computer operating system, the controller software manages the nodes, links the components, and performs internal diagnostics. The PLC system shell resides in the read-only memory of the central microchip and is always ready for operation.
The programmable controller operates in a cyclic mode by periodically collecting input information. This cycle has 4 stages:
- Polling inputs.
- Perform tasks set by the user.
- Set output parameters.
- Other auxiliary operations processes.
Classification of controllers
Regarding I/O lines, PLC controllers are classified into:
- nanocontrollers;
- microcontrollers;
- medium controllers;
- big controllers.
Regarding the location of I / O modules, they distinguish:
- monoblock;
- modular;
- distributed.
Depending on the installation method and PLC design, there are:
- panel;
- for mounting inside on a special rail;
- for wall mounting;
- rack mount;
- without housing (one board).
