What is PLC?

PLC, Programable Logic Controller is a control system which is basically a CPU connected to te integration with the input-output devices.

PLC 1756 Guardlogic by Allen Bradley

In general, PLC is used as means of controlling a machine which were previously widely used hardware devices such as relays, magnetic contactor, and so on. Currently PLC has been able to replace the relay with the ability to control the function of much more efficient and flexible. Now , there are a lot of PLC makers are widely used in industrial fields such as Siemans, Allan Bradley, Omron, Mitsubishi, Fuji, and so on.
For more clearly the following we compare the control system with relay or then we call this system " conventional system", and the machine controlled by PLC:

1. Flexibility, PLC has higher flexibility compared with conventional system, both at the beginning or at the time making the changing a process of the machine. Try to image how busy changing the wiring or circuit if the circuit will be additions or change. Similarly, if the wiring would be making the system much more complicated.
2. Space, Needed a larger space at a machine using conventional system. PLC could replace the functions performed control devices such as relays, counters, or even functions that count will minimize the required space.
3. Easy in troubleshooting, at the time the machine in trouble can easily be monitored through a software PLC that will shorten the time. As with the conventional system that must be checked one by one wiring or devices are connected.
4. Development, Now the functions of PLC not only serves as a control system, for example has been equipped with communication systems such ethernet. Different with the conventional control that simply serves as the machine control system.

From the above description especially in terms of function, it can be concluded that a lot of  advantages possessed by the PLC. However, some things must be considered when used PLC on the machine:

1. Maintenance, because PLC is electronics devices required special conditions. For example to replace backup battery periodically.
2. Backup Program , Should be kept as back up of the memory PLC error.
3. Skill, To be able in programming PLC, it takes trained, experienced or educated.
4. Cost, Consideration should be given regarding the cost, so that can be decided exactly when a machine is used PLC, or conventional system.

Thus about the PLC, and the deeper will be discussed in subsequent chapters.