A Programmable Logic Controller (PLC) is like a computer that constantly checks the state of input devices and then decides the state for output devices. It is generally used to operate machinery. Unlike computers, PLCs are not programmed but they are made to be positioned, wired and commissioned. PLCs have become one of the most important parts of manufacturing industry with time. They are easily programmed and made to withstand harsh conditions. Their importance increases in workplaces where human labor cannot work due to harsh conditions. Not only does PLC replace manual labor but, it also makes the process more efficient and error free. Considering all these facts implies that the future definitely belongs to PLCs. The efficiency of almost every process can be increased through PLCs.
Industrial usage of PLC
PLCs are designed to hold out against humidity, vibrations, noise, and extreme temperatures i.e. places where human labors find it difficult to work. They can control and monitor a large number of actuators and sensors resulting in higher productivity and a guaranteed better quality of the end product. PLCs can control computers and machines for years, without human intervention, decreasing chances of human error. They have replaced the relays, reducing the high costs associated with the relay controlled systems. PLCs are quite simple to operate and program. Nowadays, PLCs are used for mechanized job and handling in a machine, and it increases to full computerization of production process running in a factory.
Importance of PLC
Troubleshooting is made quick and easy by the PLCs, as the operation is visible on a screen. It is a matter of seconds to locate and identify a damaged part. It was not the case in the past when an error almost always meant a lot of time invested to replace the wiring of devices and panels. However, with PLC controls, changing circuit sequences or designs are quite simple and cheap. A Programmable Logic Controller has a simple programming language and its testing can be performed in a lab. Moreover, it can perform tasks that are beyond human capabilities. PLCs contain solid state switches, hence they are able to switch unlimited times between the cycles. In that way, PWM signals can be produced in addition to very complex logic. Some PLCs can be linked to a human machine interface, acting as LCD that shows useful information for the end user. PLC is modular, which means that the different types of output and inputs and can be mixed and matched to better suit the application.
PLC vs. Traditional Relay Controls
PLCs are greater in functional capabilities and power, when compared to the old relays. Relays are usually used for turning “On” or “Off” when only a few number of devices are involved but in large systems, the wiring becomes very complex and requires some training. PLCs are best to switch small control devices and handle the complicated sequencial functions. The total cost also decreases as we increase the number of functions and devices. PLCs are simple to install and any modifications can be made by reprogramming instead of changing the wires and it requires little space. The system does not need to be moved so the maintenance costs are also low. Unlike relays, PLC can perform additional functions such as analog signal processing, counting, timing etc. PLCs can copy and perform certain logical tasks that were once, done by many interconnected relays.
Today, PLCs work as integral parts of all the industrial projects; especially, where working conditions do not allow manual work. They are applicable in nearly all the industries and so, we must know more about PLCs because future belongs to them!