PLCs. First thing to remember, Programmable Logic Controllers are electronic devices that can be programmed by the supplier that supplies it or programmers who work in your company. They will customize this equipment with automatic functions according to your control needs. Another key point is that a PLC is an electronic brain that drives other components of its machinery to perform actions that could be dangerous or too slow to do manually.
Advantages of PLCs
- Flexibility. In this case a single PLC is capable of easily operating a variety of machine types.
- Correction of Errors. Before the PLCs, it was necessary that the relay frames were physically altered so that a new circuit design could be achieved. In particular with PLCs, a change in circuit design can be easily modified by simple reprogramming of the controller. Therefore, the correction of errors in the controllers is extremely short in its duration and quite economical.
- Space Efficiency. With the memory development of the PLCs, the opportunity to use contacts, coils, timers, sequencers and counters in a single controller has been greatly increased. For this reason the need for several different control panels for multiple systems it is been reduced.
- Low Cost. Surprisingly, PLC cost varies from a few hundred to a few thousand. The action of reducing the number of external components to operate a single system, through the purchase of a single PLC, can save money from direct costs and installation.
- Tests. That is to say, the program can be tested, validated and corrected with very precious time saving.
PLC applications in the industry
Certainly, PLC systems appear in different types of industrial processes. In fact, its usefulness covers many flanks, from small ones such as dispensers or forklifts, to complex control systems or complete production lines. With this in mind, you just have to choose the correct model for each case.
- Machines for the processing of gravel, cement and sand.
- Industrial machines for wood and furniture.
- Plastic machinery
- Machines – complex tools.
- Assembly machines
- Transfer machine
- Security installations
- Heating and air conditioning installations.
- Plant facilities for bottling.
- Transportation and storage facilities.
- Facilities for thermal treatments.
- Installations of the automotive industry.
- Applications in assembly lines for welding, paint booths, assembly, etc.
- Use in machine tools such as milling machines, drills, lathes, etc.
- Control of machinery for the extrusion of rubber, the assembly of covers …
- Control of refrigeration systems, vulcanized presses, etc.
Petrochemical and chemical plants
- Application in oil pipelines, refining, electrolytic baths, wastewater and wastewater treatments, etc.
- Control of processes such as weighing, dosing, mixing, etc.
Other industrial sectors
- Metallurgy: control of furnaces, foundries, rolling, cranes, forges, welding, etc.
- Food: packaging, storage, filling bottles, bottling, etc.
- Wood and paper mills: sawmills, process control, laminates, conglomerate production.
- Energy production: turbines, fuel transport, power plants, solar energy.
- Traffic: railways, traffic control and regulation.
- Home automation: room temperature, anti-theft systems, lighting, etc.
How does PLCs work?
As shown above, a programmable logic controller is a special computer which controls machines and processes. Thus, it shares a common base with the PCs, such as the central processing unit, memory, software and communications. To emphasize, the PLC is designed to survive in the toughest industrial environments and is very flexible in its interface with inputs and outputs.
To point out, PLCs come in several different formats and sizes. Some, we can accommodate them in the pocket, while the larger control systems require large PLC racks.
Power Supply and Rack
In general, the frame keeps everything together. It saves the cards for communication with the CPU. The power supply regulates the DC power for each of the modules in the rack.
This is the brain behind the PLC. Typically, you can find the CPU behind the power supply. In detail, the CPU is composed of a microprocessor, a memory chip and logic circuits for monitoring and communication. This is where the logical program is implemented, the program is executed and the process is operated.
Input / Output System [Input / Output]
In this case is where the physical connections between the equipment and the PLC are located. To put in another way, a terminal strip is used for the I / O cards, for the device connections.
The input / output system works in line with the CPU, where the input devices record and measure the data received by the monitoring components and provide information to the CPU to determine what the machine or the process should do with it . The output system transmits the execution of the program originating from the CPU for the processes and operating machines. Normally, the PLC executes a single type of execution for a specific task or process.