plc IO module operating principles and classification

PLC interface with the electrical circuit, the input and output section by the (I / O) completion. plc IO module integrates the PLC's plc IO module circuit, the input signal status register reflects the input and output points to reflect the state of the output latch. The input module signals into the electrical signals into digital PLC system, the opposite output module. plc IO module into digital input (DI), digital output (DO), analog input (AI), analog output (AO) and other modules. Commonly used plc IO module classified as follows: Switch: Press voltage level points with 220VAC, 110VAC, 24VDC, by isolating way points, with relay isolation and transistor isolation. Analog: divided by signal type, there is a current type (4-20mA, 0-20mA), voltage type (0-10V, 0-5V, -10-10V), etc., according to the accuracy of points, there are 12bit, 14bit, 16bit, etc. . In addition to the general purpose IO, there are special IO modules, such as thermal resistance, thermocouple, pulse and other modules.

plc io module is divided into several modules by function

plc IO module is divided into several modules according to function, such as CPU modules, input modules, output modules, power modules, and so on. The module features a single mainframe digital output module is more some kind of modules and therefore relatively more. This can also be said to be the trend. At present, some medium-sized plc digital input output io module machine, the module features also tend to single species also increases Township. If the same OMRON Corporation C20 series PLC, H machine CPU unit to contain the power, and put the power ceded Ha machine, a separate power supply module.

PLC's IO module input sampling stage works

PLC works: When the PLC into operation, their work is generally divided into three stages, namely the input sample, a user program execution and output refresh three stages. Completion of the three phases is called a scan cycle. During the entire operation, PLC's CPU to a scanning speed of repeating the above three phases. (A) input sampling stage: input sampling stage, PLC scan mode sequentially reads all input status and data stored within them plc analog io module image area corresponding the unit. After the end of the plc input module sample, into the user program execution and output refresh period. In both stages, and even if the input data changes state, status, and data g-input-output-module/">IO module plc of the image area of ​​the corresponding cell is not changed. Therefore, if the input is a pulse signal, the width of the pulse signal must be greater than one scanning cycle, in order to ensure that in any case, the input can be read.

input module, also known as the control module

input module, also known as the control module, when the output signal can control requirements, or to provide a switching signal to the controlled device movements, and can receive feedback signal device to the host to report to the fire alarm system is an important linkage part of the plc input module and output modules on the market can provide a pair of passive normally open / normally closed contacts for controlling the controlled device, some manufacturers of analog input module can be set via the parameter set corresponding to the active output there are pairs of input and output modules, multiple input and output modules, and so on.

Some of the role plc input output modules

Our automated industrial chain two - plc digital io module underlying field devices (especially transmitters and actuators), the upper integrated automation software is the weakest link. Our own design and manufacture of smart transmitters, only 9% of the domestic market. Top-level control software integration weak, partly because the process of industrial enterprise users do not understand the characteristics of the profound lack of experience accumulated, thereby constraining the top-level integration capabilities and quick access to intelligent micro china programmable logic controller plc market segments (industrial enterprises by the state's ability to design qualification prescribed threshold is one of the reasons). User market for their industrial technology / product does not agree, restricted independent research and development of industrial products, opportunities for improvement practices.
For these reasons, the control system made ​​it difficult to enter the critical major projects, core, major equipment, most of the analog output modules in this market is still a monopoly of foreign industrial control systems.
(B) PLC input output modules, for the majority of the discrete factory automation PLC system, the situation is not optimistic.
The current scope of application of PLC technology, in addition to covering a large chemical industry, power companies in almost all industries. However, the current application of the PLC market, more than 95 percent are from foreign products, domestic enterprises absolute disadvantage occupation.

a computer network to insert external plc IO modules.

 The main difference from other computers is that harsh conditions (such as dust, moisture, heat, cold), and a facility for extensive plc IO module arrangements PLC's armor. These PLC connected to sensors and actuators. PLC read limit switches, analog process variables (such as temperature and pressure), and a complex positioning system location. Some use machine vision. In the side of the actuator, PLC operation of the electric motor, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. Input / output configuration can be built a simple programmable logic controller, or the PLC can be attached to a computer network to insert external PLC I / O modules.
 plc digital input output io module or discrete signal performance of a binary switch, resulting in a simple on or off signal (1 or 0, True or False, respectively). Buttons, limit switches, photoelectric sensors, and a discrete signal device provides an example. Discrete signal by a voltage or current in a specific range to another are assigned to the sending off. For example, a PLC can use 24 volt DC I / O, with values ​​above 22 volts DC on behalf of the following values ​​represent 2VDC off, the middle value is undefined.