A PLC is a digital electronic device built to control machines and processes by performing event and time coding operations. PLC is built for heterogeneous industrial environments. It can be programmed without special skills in programming and can be maintained by factory technicians. You can get online coaching on PLC.
The automotive industry has introduced the PLC to eliminate the high cost of the wired, inflexible, relayed panels. The Hydromantic Division of General Motors Corporation has developed design specifications for the first logic controller programmable in 1986. They have called for a reliable and flexible numerical system that would be gifted in the industrial environment that could be easily programmed and maintained by factory staff which could be reusable. Each time the car model was changed, hundreds of wired cabinets with relays were thrown into the garbage.
Since this beginning in 1986, PLCs have developed far more than just being an inexpensive replacement of logic panels with relays. Recent PLCs include modules that perform a multitude of functions such as logic, timing, counting, sequencing, PID control, and fuzzy logic. They can perform arithmetic operations, analyze data and communicate with other programmable controllers and with server-type computers.
Some advantages of PLCs include:
- A PLC can handle many different operations, and changes are made at software level and are easier to implement than hardware changes.
- Electronic devices are safer and easier to maintain than timers and mechanical relays.
- Lower cost. The advantage of PLC comes from the ability of numerical systems to achieve more complex functions at a lower cost.
- PLC programming equipment can provide a listing immediately on the current control circuit.
The tendency in industrial control is to use smaller PLCs next to the process instead of centralized PLCs with many inputs and outputs. A supervisor computer communicates with individual PLCs over a local area network (LAN) to coordinate their activities. One reason for imposing this trend is the very complex program required to control a centralized system with a large PLC. By dividing the process into smaller and easier to administer, specialists will recognize this theory as an application of a proven technique to solve a problem called divide and mastery. This method solves difficult problems by dividing them into a number of smaller problems and easier to solve. You can read more here.
The most important functional components that can fit in the PLC configuration are
- Power supply;
- Processor module;
- Entry modules;
- Output modules;
- The programming unit;
- PID controller unit;
- Data communication unit.
The notion of PLC comes from Programmable Logic Controller (Programmable Logic Controller) and is a digital computer used to automate industrial processes.
These processes, which PLCs can control, are very diverse, such as transport systems (conveyors), the food industry machine, automotive assembly lines. Their programming is done using the digital technique.
In the past, people were the main method to control a system. Now, in our times, electricity is used for control, and this control is based on electrical relays. These relays allow the interruption or supply of energy without the use of mechanical switches.
The development of low-cost computers has led to the revolutionary emergence of PLCs (programmable controllers). The advances in technology on a very large scale have led to the possibility of real-time simulation of many applications in the industrial field.
Real-time simulations are very useful when programming a technological process, preventing or removing possible system malfunctions and / or bottlenecks that may temporarily destroy or temporarily affect components.
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According to the National Electrical Manufacturers Associations (NEMA), a PLC is the microprocessor-based solution that uses sensor-connected input modules to read the state of the controlled system, change the system state task analysis, and clarify consecutive actions, and finally, uses the output modules to guide conductors and actuators. Therefore, the PLC’s software task consists in calculating the correct output values, giving a picture of the input values.
The flexibility, reliability, insensitivity to interference, and a number of requirements for the facilities offered to introduce or modify work schedules are just some of the basic features currently required for leading equipment for most applications.