Analog I/O Modules of PLC Earlier PLCs were limited to discrete or digital I/O interfaces, which allowed only on/off-type devices to be connected. This limitation meant that the PLC could have only partial control of many process applications. Today, however, a complete range of both discrete and analog interfaces are available that will allow controllers …
Discrete I/O Modules of PLC The most common type of I/O interface module is the discrete type ( Figure 1). This type of interface connects field input devices of the ON/OFF nature such as selector switches, pushbuttons, and limit switches. Likewise, output control is limited to devices such as lights, relays, solenoids, and motor starters that …
Input Output Section of PLC The input output section of PLC is the section to which all field devices are connected and provides the interface between them and the CPU. Input/output arrangements are built into a fixed PLC while modular types use external I/O modules that plug into the PLC. Figure 1 illustrates a rack-based …
Parts of Programmable Logic Controller A typical PLC can be divided into parts, as illustrated in Figure 1. These are the central processing unit (CPU), the input/output (I/O) section, the power supply, and the programming device. The term architecture can refer to PLC hardware, to PLC software, or to a combination of both. An open …
Programmable logic controllers are now the most widely used industrial process control technology. A programmable logic controller (PLC) is an industrial grade computer that is capable of being programmed to perform control functions. The programmable controller has eliminated much of the hardwiring associated with conventional relay control circuits. Other benefits include easy programming and installation, …
