output module plc in control system

Programmable controller (Programmable Logic Controller) referred to a PLC or PC, is developed from the early relay logic control system, which constantly absorbing micro- computer technology to  Nanda analog output plc continuously enhance the functionality gradually suitable for complex control tasks.
 PLC viable reason is that it is more suitable for industrial field and market requirements : high reliability , simple and strong anti- interference of various programming installation, low price and long life. Than the microcontroller, its input and output ports closer to the field devices , without adding too much of the middle part or need more interfaces , so saving the plc input output modules  user time and cost. PLC lower end (input side ) of the relay , a transistor and thyristor control means for the user while the upper end is usually a microcomputer . When people use it , you can not carry out specialized training in computers , programmable controllers can be operated and programmed. Used to perform a variety of different levels of complexity of industrial control tasks. It began with a wire connected to it subtly with switching devices constitute or use different logic control sequence control . So far, the PLC programming languages ​​- Ladder can also see the shadow of the wiring . Until the late 1960s , early 1970s, the advent of the programmable controller , with the rapid development of microelectronics technology, computer technology and data communications technology, and the emergence of the  plc soe module microprocessor , PLC products towards small and ultra- miniaturization conducted a leap , and finally to the early PLC from the initial logic control, sequence control , PLC has developed into a modern logic, timing, counting , memory and arithmetic operations , data processing, communications and networking functions such as PID loop controller .