Monday 9 December 2013

The Definition. What Is PLC?

By Samuel Akinwumi


What is a PLC? A programmable controller, or Programmable Logic Controller (PLC) is a device which is capable of being programmed to perform a controlling function. Before the advent of the programmable controller, the problem of industrial control was usually solved by the use of electromechanical relays or by hardwired solid-state logic blocks. These systems were very flexible in design and easy for maintenance personnel to understand. However, they involved a vast amount of interconnection from relay to relay, and logic block to logic block. In order for the wiring cost to be minimized, relays and logic blocks had to be kept close together. This led to the development of the control panel concept for larger and more complex logic control systems.

An additional essential aspect within the improvement from the manage solar panel had been a chance to examine area products in a typical stage. The manage program along with 1000 pushbuttons, as well as result products might very easily include an extremely big region inside a manufacturing facility. Therefore, it might consider a great deal of period for any specialist to check on every gadget from it's area. With every gadget " cable " to a typical stage, every gadget might be examined with regard to procedure rapidly.

What is a PLC? Programmable controllers were originally designed to provide flexibility in control based on programming and executing logic instructions. Major advantages were realized by adopting the ladder diagram programming language, simplifying maintenance, and reducing the cost of spare parts inventories. Also, programmable controllers allow for shorter installation time and faster commissioning through programming rather than wiring.

In recent years, one of the areas of greatest growth and innovation has been in data communication for PLCs. PLC technology has been adopting the expanding resources of information and communication technology such as wireless local area networks (WLAN). Initially, each manufacturer had their own proprietary system whereby one could remotely interact with the PLC to monitor status and data. These days PLCs are more and more becoming compatible with standards- based communications systems such as Ethernet, Profibus, DeviceNet, and Genius networks. This means that the PLC can be hooked up to any other device on the factory floor that can communicate through these networks.

Ethernet is commonly used for interconnecting information and communication networks in the office, so the PLCs can be monitored and controlled from anywhere in a building. And not only that - they can be accessed from anywhere in the world via modem and telephone line. The newest trend is enabling control and monitoring over the Internet by using a Web browser such as Internet Explorer

What is PLC? Modern PLCs are very similar to personal computers in their size, speed, and memory capacity. Recent innovations in flash memory and LCD-screen technology has greatly improved the memory storage and graphic user interface capabilities of these systems, allowing for a wider range of programming applications and greater flexibility in programming languages. With the IEC-61131-3 standard, it is now possible to program these devices using structured programming languages (such as C), and logic elementary operations. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers.

The following points outline some of the other numerous advantages derived from using PLCs:

1. Programmable controllers tend to be simple to plan and also to set up. The majority of PLCs are supplied along with quick- discharge kind mess cable connections with regard to quick cabling associated with enter as well as result products. PLC modifying functions permit plan modifications, modifications, as well as launching methods to become achieved within mere seconds generally.

2. The speed with which internal timers operate is much faster than conventional time delay relay systems. For example, a typical time delay relay can produce a short delay as fast as 150 milliseconds (ms), with a reset period of 300 ms. A PLC can produce a short delay of 15 ms, with a reset period of approximately 15 ms. In terms of a speed difference between the two systems, a PLC is roughly 13 times faster. An assembly machine using a PLC would therefore have a higher productivity rate.

3. Access to PLCs is restricted by hardware features such as keylocks, and by software features, such as passwords. Timers and their timing values can also be protected through special commands

4. Problem solving with PLCs is also a major advantage over any other type of control system. Many PLCs are provided with diagnostic indicators which monitor power supply, central processing unit faults, low battery power for memory backup, input and output conditions, forced output conditions, and so on.

5. Programmable controllers can be designed with communications capabilities that allow them to converse with local and remote computer systems or to provide human interfaces. These interfaces range from simple light or annunciator systems with alpha- numeric displays to elaborate video screens that allow the current state of a process to be viewed.

6. PLCs are extremely reliable control devices and can be obtained in forms that can survive and function in harsh conditions. They can meet almost any set of installation code requirements.

What's PLC? Whilst the benefits of utilizing PLCs when compared with conventional exchange manage techniques are very obvious, recently one of many rivals towards the PLC may be using pcs within commercial programs. Because you will notice within following quests, you will find a lot of commonalities in between PLC as well as pc equipment. Nevertheless, there's also a few unique benefits related to PLCs in comparison with pcs as well as these types of benefits consist of:

A large base of trained maintenance personnel experienced in troubleshooting and servicing systems with ladder logic programming, rather than personal computer software languages such as Visual Basic, C++, HTML, etc.

More effective response to power interruptions and failures

Cost advantages for simple machine control applications

Higher reliability that minimizes the expense of shutdown, troubleshooting, repair, & startup

Durable, weather-proof, industrial strength packaging

Lengthy accessibility as well as assistance with regard to item versions with no quick obsolescence typical within pcs.

What is a PLC? A digitally operated electronic apparatus which uses a programmable memory for the internal storage of instructions for implementing specific functions such as logic, sequencing, timing, counting, and arithmetic, to control, through digital or analog input/output modules, various types of machines or processes.




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