5SHX08F4502? ABB 可編程邏輯控制器或 PLC 在當(dāng)今的各種流程和制造行業(yè)中無處不在。PLC 最初旨在取代機(jī)電繼電器系統(tǒng)，以便為修改控制系統(tǒng)的操作提供更簡單的解決方案。無需重新連接大量繼電器，只需從 PC 或編程設(shè)備快速下載，即可在幾秒鐘內(nèi)更改控制邏輯。PLC 是一種工業(yè)級數(shù)字計(jì)算機(jī)，旨在執(zhí)行控制功能，尤其適用于工業(yè)應(yīng)用。

5SHX08F4502

今天的大多數(shù) PLC 都是模塊化的，允許用戶添加各種功能，包括離散和模擬輸入和輸出、PID 控制、位置控制、電機(jī)控制、串行通信和高速網(wǎng)絡(luò)。與繼電器組等較舊的技術(shù)相比，PLC 更易于故障排除和維護(hù)、更可靠、更具成本效益且用途更廣泛。Modicon 是“模塊化數(shù)字控制器”的縮寫，它既是1968 年發(fā)明的第一個 PLC 產(chǎn)品的名稱，也是發(fā)明它的品牌，盡管現(xiàn)在歸施耐德電氣所有。
雖然5SHX08F4502? ABB 可編程邏輯控制器可能看起來不像典型的家用計(jì)算機(jī)，但 PLC 的核心與大多數(shù)人在日常生活中使用的計(jì)算機(jī)和智能設(shè)備中所見的技術(shù)完全相同。

5SHX08F4502

基本組件PLC由幾個基本部分組成。它們可能看起來與各個制造商略有不同，但每個組件的用途和范圍是相同的。其中包括電源、中央處理單元 (CPU)、輸入/輸出卡以及放置輸入/輸出 (I/O) 卡的背板或機(jī)架。如圖 2 所示，背板在所有獨(dú)立組件之間建立了電氣連接，從而為 PLC 提供了模塊化設(shè)計(jì)。這種電連接包括電源和通信信號。許多 PLC 制造商在背板上使用專有通信協(xié)議，以便 I/O 可以安全地與 CPU 通信。電源根據(jù)應(yīng)用和安裝環(huán)境，電源可接受 120VAC 或 24VDC。如上所述，此電壓通過背板為 CPU 和 I/O 模塊提供電源，這些模塊以“卡”的形式出現(xiàn)。這些卡可以從它們在載體中的插槽中快速添加或移除。需要注意的是，CPU 的電源并不為傳感器和線圈等現(xiàn)場設(shè)備供電。此電源連接必須單獨(dú)與卡建立。
5SHX08F4502? ABB 可編程邏輯控制器中央處理器 (CPU)CPU 是 PLC 的實(shí)際“大腦”，使其成為計(jì)算機(jī)。即使是小型的非模塊化 PLC 也包含一個 CPU。輸入信號來自 I/O 卡，邏輯程序根據(jù)信號做出決策。如果需要，CPU 然后命令輸出隨著信號和條件的變化而打開和關(guān)閉。程序可能包括高級功能，例如數(shù)學(xué)運(yùn)算、計(jì)時(shí)、計(jì)數(shù)和通過現(xiàn)代網(wǎng)絡(luò)協(xié)議共享信息。對于較舊的中繼系統(tǒng)，其中許多操作即使不是不可能，也是極其困難的。
5SHX08F4502? ABB 可編程邏輯控制器輸入/輸出卡傳感器、按鈕、開關(guān)、繼電器、螺線管甚至網(wǎng)絡(luò)設(shè)備與連接到 I/O 卡上的螺絲端子的 I/O 信號共享信息?？梢愿鶕?jù)每臺機(jī)器和設(shè)??施的需要選擇這些卡。在一些小型 PLC中，I/O 端子不是模塊化卡，而是方便地安裝在 PLC 的側(cè)面。由于 I/O 設(shè)備結(jié)構(gòu)種類繁多，分立和模擬模塊的種類繁多，模擬模型的術(shù)語有“源”與“灌”，“電壓”與“電流” 。編程設(shè)備和人機(jī)界面PLC 本身之外有兩個非常重要的組件：編程設(shè)備和人機(jī)界面 (HMI)。編程設(shè)備可以是來自同一制造商的臺式計(jì)算機(jī)、膝上型計(jì)算機(jī)或手持式儀器。一些小型 PLC 甚至在前面有按鈕，可以在不需要計(jì)算機(jī)的情況下對非常基本的邏輯操作進(jìn)行編程。

5SHX08F4502

5SHX08F4502 ABB programmable logic controllers or PLCS are ubiquitous in a wide variety of processes and manufacturing industries today. PLCS were originally designed to replace electromechanical relay systems in order to provide a simpler solution for modifying the operation of control systems. Instead of reconnecting a large number of relays, you can quickly download them from a PC or programming device and change the control logic in seconds. A PLC is an industrial-grade digital computer designed to perform control functions and is particularly suitable for industrial applications.
Most PLCS today are modular, allowing users to add a variety of functions, including discrete and analog inputs and outputs, PID control, position control, motor control, serial communication, and high-speed networking. PLCS are easier to troubleshoot and maintain, more reliable, more cost-effective, and more versatile than older technologies such as relay groups. Modicon, short for “modular digital controller,” is both the name of the first PLC product invented in 1968 and the brand that invented it, although it is now owned by Schneider Electric.
While the 5SHX08F4502 ABB Programmable logic controller may not look like a typical home computer, the core of the PLC is exactly the same technology that most people see in the computers and smart devices they use in their daily lives.
Basic components PLC consists of several basic components. They may look slightly different from individual manufacturers, but the purpose and scope of each component is the same. These include the power supply, the central processing unit (CPU), the input/output card, and the backplane or rack that houses the input/output (I/O) card. As shown in Figure 2, the backplane establishes electrical connections between all the individual components, thus providing a modular design for the PLC. This electrical connection includes a power supply and a communication signal. Many PLC manufacturers use proprietary communication protocols on the backplane so that I/O can securely communicate with the CPU. Power Supply Depending on the application and installation environment, the power supply can accept either 120VAC or 24VDC. As mentioned above, this voltage supplies power to the CPU and I/O modules through the backplane, which come in the form of “cards.” These cards can be quickly added or removed from their slots in the carrier. It should be noted that the CPU’s power supply does not power field devices such as sensors and coils. This power connection must be established separately from the card.

5SHX08F4502

5SHX08F4502 ABB Programmable Logic Controller Central Processing Unit (CPU) The CPU is the actual “brain” of the PLC, making it a computer. Even small non-modular PLCS contain a CPU. The input signal comes from the I/O card, and the logic program makes decisions based on the signal. If needed, the CPU then commands the output to turn on and off as signals and conditions change. Programs may include advanced functions such as mathematical operations, timing, counting, and sharing information over modern network protocols. Many of these operations are extremely difficult, if not impossible, for older relay systems.
5SHX08F4502 ABB Programmable Logic Controller Input/output card sensors, buttons, switches, relays, solenos and even network devices share information with the I/O signals connected to the screw terminals on the I/O card. These cards can be selected according to the needs of each machine and device. In some small PLCS, the I/O terminals are not modular cards, but are conveniently mounted on the side of the PLC. Due to the wide variety of I/O device structures and the wide variety of discrete and analog modules, the terms of the simulation model are “source” and “perfusion”, “voltage” and “current”. There are two very important components outside the PLC itself: the programming device and the Human Machine interface (HMI). The programming device can be a desktop computer, laptop, or handheld instrument from the same manufacturer. Some small PLCS even have buttons on the front that allow very basic logic operations to be programmed without the need for a computer.