After invention of transistors and integrated circuits (ICs), and with the rapid advancement of computer science and technology, the design and implementation of hardware is possible through programmable software, which allowed the action for commands of each person in the relevant circuit; it gradually became standard with the PLC or PLAY PROGRAMABLE LOGIC CONTROLER.

Therefore, PLC is an instrument issues the necessary commands in the appropriate outputs based on the existing sensors (SENSORS) and the processing of the working environment through input signals and the analysis of the data in accordance with the given program; in other words, the PLC is the brain of System and control in today's industry. So, old boards full of relays, connectors, timers, and switches replace by PLC and lower-volume panels and less physical wiring, but with excellent data flexibility. The main advantage of the PLC is its programmability, which makes the PLC more flexible and efficient, so it can be used in the various industries, even the aerospace. In Any industry, a PLC program based on the needs, will be written and installed on it.

PLC capabilities that evolved throughout the time are sequential relay control, motion control, process control, distributed control systems, and networking. Examining data, storage, processing power, and communication capabilities of some modern PLCs are equivalent to desktop computers. Similar PLC programming, along with input hardware - remote control output, has made extensive use of PLCs. In general, since the desktop computer runs on platforms with less stability than PLCs, and also because desktop computer hardware typically has the normal level of temperature tolerance, moisture, vibration, and life span of the LCD PC hardware which are not designed for that purpose, the use of desktop computers in the heavy industry is not accepted. Another reason for using PLC is, the cost of computers comparing to PLC.

Keywords: Electronic Command Reconstruction - PLC

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