可編程控制器是60年代末在美國首先出現(xiàn)，當時叫可編程邏輯控制器PLC（ProgrammableLogicController），目的是用來取代繼電器，以執(zhí)行邏輯判斷、計時、計數(shù)等順序控制功能。PLC的基本設(shè)計思想是把計算機功能完善、靈活、通用等優(yōu)點和繼電器控制系統(tǒng)的簡單易懂、操作方便、價格便宜等優(yōu)點結(jié)合起來，控制器的硬件是標準的、通用的。根據(jù)實際應(yīng)用對象，將控制內(nèi)容編成軟件寫入控制器的用戶程序存儲器內(nèi)?？刂破骱捅豢貙ο筮B接方便。

? ? 隨著半導(dǎo)體技術(shù)，尤其是微處理器和微型計算機技術(shù)的發(fā)展，到70年代中期以后，PLC已廣泛地使用微處理器作為中央處理器，輸入輸出模塊和外圍電路也都采用了中、大規(guī)模甚至超大規(guī)模的集成電路，這時的PLC已不再是邏輯判斷功能，還同時具有數(shù)據(jù)處理、PID調(diào)節(jié)和數(shù)據(jù)通信功能。

? ? 可編程控制器是一種數(shù)字運算操作的電子系統(tǒng)，專為在工業(yè)環(huán)境下應(yīng)用而設(shè)計。它采用了可編程序的存儲器，用來在其內(nèi)部存儲執(zhí)行邏輯運算，順序控制、定時、計算和算術(shù)運算等操作的指令，并通過數(shù)字式和模擬式的輸入輸出，控制各種類型的機械或生產(chǎn)過程。PLC是微機技術(shù)與傳統(tǒng)的繼電接觸控制技術(shù)相結(jié)合的產(chǎn)物，它克服了繼電接觸控制系統(tǒng)中機械觸點的接線復(fù)雜、可靠性低、功耗高、通用性和靈活性差的缺點，充分利用微處理器的優(yōu)點。

? ? 可編程控制器對用戶來說，是一種無觸點設(shè)備，改變程序即可改變生產(chǎn)工藝，因此可在初步設(shè)計階段選用可編程控制器，在實施階段再確定工藝過程。另一方面，從制造生產(chǎn)可編程控制器的廠商角度看，在制造階段不需要根據(jù)用戶的訂貨要求專門設(shè)計控制器，適合批量生產(chǎn)。由于這些特點，可編程控制器問世以后很快受到工業(yè)控制界的歡迎，并得到迅速的發(fā)展。目前，可編程控制器已成為工廠自動化的強有力工具，得到了廣泛的應(yīng)用。

Programmable controller is 60 s first appeared in the United States, was called a programmable logic controller PLC (ProgrammableLogicController), the purpose is to replace relay, to perform logic, timing, counting and other sequence control function. The basic design idea of PLC is to combine the advantages of computer function perfect, flexible and universal and the advantages of relay control system simple and easy to understand, easy to operate and cheap, and the hardware of the controller is standard and universal. According to the actual application object, the control content is compiled into software and written into the user program memory of the controller. Easy connection between controller and controlled object.
With the development of semiconductor technology, especially microprocessor and microcomputer technology, after the mid-1970s, PLC has been widely used as a central processor, input and output modules and peripheral circuits are also used in the medium, large-scale or even very large scale integrated circuits, then the PLC is no longer a logical judgment function. It also has the functions of data processing, PID regulation and data communication.
A programmable controller (PLC) is a digital arithmetic operated electronic system designed for use in industrial environments. It uses a programmable memory to store instructions for performing operations such as logical operations, sequence control, timing, calculation and arithmetic operations, and to control various types of machinery or production processes through digital and analog inputs and outputs. PLC is a combination of microcomputer technology and traditional relay contact control technology, it overcomes the shortcomings of complex connection, low reliability, high power consumption, versatility and flexibility of the mechanical contact in the relay contact control system, and makes full use of the advantages of the microprocessor.
For the user, the programmable controller is a contactless device, and the production process can be changed by changing the program, so the programmable controller can be selected in the preliminary design stage and the process can be determined in the implementation stage. On the other hand, from the point of view of the manufacturer of programmable controller, it is not necessary to design the controller according to the user’s order requirements in the manufacturing stage, which is suitable for mass production. Because of these characteristics, the programmable controller was soon welcomed by the industrial control community after its advent, and has been rapidly developed. At present, programmable controller has become a powerful tool for factory automation and has been widely used.